reproducerea artificiala la salau

Controlled reproduction of pikeperch Sander lucioperca (L.):a review

Received 30 April 2009/Accepted 22 June 2009. Published online: 30 December 2009; Inland Fisheries Institute in Olsztyn, Poland

Zdzisaw Zak, Krystyna Demska-Zak

Abstract. Mastering techniques for conducting the controlledreproduction of a given fish species, the procedures for performinghormonal stimulation, and the choice of the appropriate hormonalpreparation and dosage all have a significant impact on theeffectiveness of spawning, and, in turn, on the quantity of stockingmaterial produced. This paper presents reproduction techniquesfor pikeperch, one of the most economically valuable species offreshwater European fish. The methods discussed include cagespawning, the artificial reproduction of wild fish (obtained fromthe natural environment), and out-of-season spawning. Theprinciples of stimulating spawning with either photothermal orhormonal methods are also described. It is demonstrated thatusing in vivo methods for determining the maturation stage ofoocytes and hormonal stimulation (especially in less maturefemales) permits increasing cage and artificial spawning of wildfish. Among the hormones and hormonal preparations tested todate in the artificial spawning of pikeperch (gonadotropins (GtH),gonadoliberins (GnRH), and synthetic analogues (GnRHa)), themost effective have been carp pituitary extract (CPE) and humanchorionic gonadotropin (hCG). This paper also presents the mostrecent techniques used in the production of pikeperch stockingmaterial.

Keywords: pikeperch, cage spawning, artificialreproduction, out-of-season spawning, hormonalstimulation

Introduction

Pikeperch, Sander lucioperca (L.), is a highly valuedfish in Europe thanks to the organoleptic qualities ofits meat (Dil 2008). The supply of pikeperch, how-ever, has decreased drastically, and in the past fiftyyears catches of it from natural waters has declinedfour-fold (FAO 2007). This species is also very popu-lar among recreational fishers (Bninska and Wolos2001). Consequently, the demand for pikeperchstocking material for both stocking programs in natu-ral waters and for intensive culture is continually in-creasing. Pikeperch is currently being cultivated inseveral European fish farms in recirculation systems(RAS) using commercial feed (Philipsen 2008). Theincreasing demand for stocking material and thehighly variable effectiveness of methods used to datefor the artificial reproduction of pikeperch haveprompted several groups of scientists to study andthen develop more effective methods for reproducingthis species, and, as a consequence, increase the pro-duction of stocking material.

The challenges presented by the controlled re-production of pikeperch have long inspired ichthyol-ogists. The first reports of attempts to obtain the sexproducts of this species date to the nineteenth cen-tury (Sakowicz 1928). However, to date the methodsusually used to accomplish this are either naturalspawning or semi-natural spawning conducted inearthen ponds (Wojda et al. 1994, Steffens et al.1996, Wojda 2006). Fertilized pikeperch eggs are

Arch. Pol. Fish. (2009) 17: 153-170DOI 10.2478/v10086-009-0014-z

REVIEW PAPER

Z. Zak []Department of AquacultureThe Stanisaw Sakowicz Inland Fisheries Institute in OlsztynOczapowskiego 10, 10-719 Olsztyn, PolandTel. +48 89 5241029, e-mail: [email protected]

K. Demska-ZakDepartment of Ichthyology,University of Warmia and Mazury, Olsztyn, Poland

also obtained by deploying various types of artificialnests in the natural spawning grounds of this species(Korycki 1976, Horvth et al. 1984). Another way toobtain eggs is to conduct pikeperch spawning inearthen ponds equipped with spawning nests madeof various materials (Horvth et al. 1984, Wojda et al.1994, Ciela et al. 1996, Wojda 2006). Spawningnests are also deployed in a rare method of pikeperchreproduction known as lake cages (e.g., Kieczewski1939, Terlecki 1955, Korycki 1976, Antila et al.1988, Salminen et al. 1992, Craig 2000,Demska-Zak and Zak 2002). Prior to stockingthe ponds or cages with fish they are stimulated withhormonal preparations; this procedure is usuallyperformed on females (Horvth et al. 1984).

The history of fish reproduction aided by hor-monal stimulation dates to the early twentieth cen-tury. This is when fresh (and slightly later preserved) fish pituitary extract was used to stimu-late reproduction (Houssay 1930). Despite the pas-sage of time, this pituitary extract homogenate(mainly from carp, Cyprinus carpio L.) remains oneof the most commonly applied hormonal prepara-tions in aquaculture (Zohar and Mylonas 2001). Themain active ingredient in these is gonadotropins(GtH), which plays a key role in the stimulation of thesynthesis of the sex steroids, gamete maturation, andovulation and spermiation. In addition to carp pitu-itary extract (CPE), human chorionic gonadotropin(hCG) is also used successfully in fish reproduction.Other gonadotropins, such as pregnant mare serumgonadotropin (PMSG) or composite preparationscontaining pituitary and placental GtH have notfound wider applications. It should be mentionedthat PMSG is commonly used in the reproduction ofdomesticated animals such as cattle, sheep, and rab-bits. This preparation has a similar influence as dothe pituitary gonadotropins of FSH (follicle stimulat-ing hormone) and LH (luteinizing hormone).

The development of studies in the field of veteri-nary endocrinology and reproductive techniques hasspurred interest in the gonadoliberins (GnRH, formerlyLHRH). This hypothalamus hormone (decapeptide)controls the pituitary gland and stimulates it to secreteGtH. In aquaculture, applications have also been found

for natural gonadoliberins (mammalian mGnRH orsalmon sGnRH), as well as their synthetic analogues(GnRHa/LHRHa) (Peter et al. 1993, Crim and Bettles1997). The latter often differ from the natural GnRHamino acid sequence (especially in position 6), thelength of the peptide chain (they can be nonapeptides)as well as in activity. The most frequently used syn-thetic GnRH analogues include the following:D-Ala6Pro9NEt-mGnRH; D-Ala6desGly10-mGnRH;D-Phe6-mGnRH; D-Trp6-mGnRH; D-Arg6Pro9NEt-sGnRH; D-Lys6-sGnRH. In some fish species, the intro-duction of exogenous GnRH causes increased dopa-mine secretion that inhibits the effects ofgonadoliberins (Peter et al. 1993, Zohar and Mylonas2001). The negative influence of dopamine can becounteracted by applying dopamine receptor inhibitors(e.g., metoclopramide, domperidone, reserpine,pimozide). These types of substances, besidesGnRH/GnRHa, are also included in mixed prepara-tions. One of the most widely applied mixed prepara-tions is Ovopel (D-Ala6Pro9NEt-mGnRH andmetoclopramide; Horvth et al. 1997).

The aim of this paper is to summarize the mostimportant achievements in controlled pikeperch re-production techniques, the principles of stimulatingspawning, the application of hormonal preparations,and wide-ranging hatchery techniques for this eco-nomically and ecologically important species.

Spawning in cages

Pikeperch is an atypical species among Europeanfreshwater fish because it spawns in nests, and thispeculiarity was exploited in techniques of controlledreproduction in cages. The development of this re-production method also exploited the plasticity ofthis species with regard to the substrate on which itreleases its eggs; pikeperch uses either mineral(sand, gravel) or vegetation substrates(Schlumberger and Proteau 1996, Lappalainen et al.2003). Vegetation substrate is mainly used to buildspawning nests for lake cages reproduction (Steffenset al. 1996, Zak and Demska-Zak 2001, Zak

154 Zdzisaw Zak, Krystyna Demska-Zak

2009). Pikeperch spawners are caught during thepre-spawning season or at spawning grounds. De-pending on latitude, the natural spawning periodranges from April to June (Korycki 1976, Ruuhijrviand Hyvrinen 1996, Lappalainen et al. 2003). It isrecommended to use trap gear (fyke-nets) to catchspawners (Antila et al. 1988, Ruuhijrvi andHyvrinen 1996, Demska-Zak and Zak 2002).

Spawning cages are constructed with framesbuilt of wooden slats, plastic pipes, metal rods, andthe walls are usually made of netting material witha mesh bar length of about 10 mm. The shape of thecages is either rectangular (Korycki 1976,Demska-Zak and Zak 2002) or tubular (Antila etal. 1988, Salminen et al. 1992, Ruuhijrvi andHyvrinen 1996). The cages used in Poland in the1950-1970 period were known as Swedish cageswith dimensions of 1.20 (L) 0.60 (W) 0.80 (H)m. They were comprised of a holding cage for thespawners, and a lower part comprised of the spawn-ing mattress (1.20 (L) 0.60 (W) 0.10 (H) m)made of natural substrate (e.g., juniper branches androots from willows, alders). The cages were securedto piers in lakes (Korycki 1976), and were stockedwith one set of spawners each (1+ 1-2). Unfortu-nately, there is a no documented data on the effec-tiveness achieved with this method. It is known,however, that because of the small size of Swedishcages (volume 0.6 m3), eggs were often deposited inthick layers on the substrate. This often led to highmortality rates during further development becauseof insufficient gas exchange and the development ofSaprolegnia sp.

Steffens et al. (1996) recommend using largercages (volume 30-50 m3) for pikeperch reproduc-tion. It is also recommended to use larger spawningnests (1.8 (L) 0.7 (W) m; surface area 1.26 m2)(Schlumpberger and Schmidt 1980). The spawnersare usually stocked into such cages at a density of2-5 and 4-10 , and spawning usually occurs aftertwo to three days. Hormonal stimulation is used veryrarely, but if it is, it generally contains GtH. Usually,the nests and the fertilized eggs are removed to thehatchery, where the larvae hatch (recommended wa-ter temperature 16-20C; Steffens et al. 1996).

Salminen et al. (1992) used tube-shaped floatingcages with a diameter of 1.5 to 2.5 m and a height of2.0 to 2.5 m (made of netting material with a meshbar length range of 6.0 to 10.0 mm) to reproducepikeperch. The cages were fitted with spawning nestsmade of 2.0 mm-thick perforated aluminum sheetswith rice hay as the substrate. The size of the nestshould correspond to that of the female, although thenests used were usually square in shape with a sur-face area of 0.16 or 0.42 m2 (Salminen andRuuhijrvi 1991). Erm (1981, cited by Lappalainenet al. 2003) reported that the mean diameter of natu-ral pikeperch nests is approximately 0.5 m, thus, us-ing square spawning nests of the size reported bySalminen and Ruuhijrvi (1991) of 0.42 m2 (0.65 (L) 0.65 (W) m) should be allow pikeperch females todeposit their eggs. It was confirmed, however, thateven nests with a surface area of 0.4 m2 were toosmall for the larger females to spawn in (body weight> 2.5 kg). Salminen and Ruuhijrvi (1991) suggestthat each cage should contain one nest and bestocked a maximum of 3 and 4 . The period dur-ing which the fish are held in the cages for the pur-pose of spawning is usually within the range of 6 to13 days, but females can begin to spawn after asmany as 40 days (Salminen et al. 1992). The nestswith fertilized eggs are removed to empty incubationcage. One day before hatching, they were transportedto the hatchery or ponds. This method usually pro-duced an average of 80-90 thousand larvae 1 kg-1 offemale body weight (Salminen et al. 1992).

The results of the study by Salminen et al. (1992)indicates that pikeperch spawning in lake cages ex-tended over time. This might have been due to thevaried degree of maturity of the fish used for repro-duction. It was confirmed that even individualscaught in the same basin could have gonads in dis-tinctly different stages of maturity (Antila et al.1988). No hormonal stimulation was applied in thestudies by Salminen et al. (1992), and this couldhave influenced the time period during which the fishwere held in the cages. Greater spawning synchroni-zation could be obtained by using hormonal injec-tions (Demska-Zak and Zak 2002). The effects ofhormonal stimulation with GnRHa (5 g D-Ala6 Pro9

Controlled reproduction of pikeperch Sander lucioperca (L.): a review 155

NEt-mGnRH kg-1 b.w.) exclusively or in combinationwith hCG (500-2500 IU hCG kg-1 b.w.) was studiedby Antila et al. (1988). The fish were administeredthe hormones by intramuscular injection in eitherone or two doses (time interval between injectionswas 48 h). What is significant is that the studies wereconducted under similar climate (southern Finland)and technical (cylindrical lake cages) conditions asthose by Salminen et al. (1992). Each cage (1.8 m di-ameter, 1.8 m deep) was fitted with from 1-3 squarenests with a surface area of 0.20 m2 (0.45 0.45 m;rice hay substrate) and from 1-3 and 2-6 . It wasconfirmed that the percentage of ovulating females inthe group that was stimulated hormonally was higherthan that in the control group (25.0-37.5% versus0.0-11.1%). However, hormonal stimulation was notnoted to have had a significant influence on the tim-ing of spawning (the length of time the pikeperch fe-males were held in cages until spawning). In thegroup that were stimulated hormonally, the latencytime in subsequent years ranged from 2.7 to 3.8days, while in the control group the average time pe-riod was 3.5 days. Higher spawners mortality wasnoted in these studies. Female mortality was higherin the group that was stimulated hormonally(counted to the fifth day of holding the fish) than in

the control group (31.3-36.4% versus 10.5-11.1%).Antila et al. (1988) confirmed that the effect of hor-monal injections depends on the maturation stage ofthe female pikeperch, and that hormonal stimulationhas a positive effect on females whose oocytes are inthe final stage of maturation. These authors also rec-ommend a minimum of two injections of GnRHa orGnRHa and hCG.

The application of methods for determining thematurity stage of females can improve the effective-ness of controlled pikeperch reproduction. The basiccondition for performing this is that the method is invivo and that it allows for determining the maturity ofthe eggs quickly. A relatively non-invasive methodfor doing this to use a catheter passed into the ovarythrough the genital opening and suctioning outa sample of oocytes (Rothbard and Yaron 1995). Thismethod was developed initially for carp, but it can beused successfully to determine the maturity stage offemales of other species, including pikeperch(Steffens et al. 1996, Demska-Zak and Zak2002, Zak and Szczepkowski 2004,Mller-Belecke and Zienert 2008). The in vivomethod for collecting oocytes is presented in Photo 1.The oocyte sample is placed in a test tube with thepreservative and fixing Serra solution (ethyl alcohol


Photo 1. Collecting samples of oocytes from female pikeperch with a catheter.

96%:formalin:glacial acetic acid, 6:3:1, v/v) (Brzuska

and Bieniarz 1977). With pikeperch, the fixing time

lasts from 20 to 170 s depending on the maturity

stage of the sex cells (Zak and Demska-Zak

2001). Following this, the oocytes can be examined

under a microscope to determine their maturity. The

main evaluation criteria are the placement of the cell

nucleus and the degree of lipid drop dissipation.

Oocytes in the first stage of maturation have a cen-

trally-located nucleus, and the lipid drops are dissi-

pated throughout the cytoplasm (Photo 2a). Oocytes

with nuclei that have shifted past the center of the cell

are classified as stage II. The lipid drops are less nu-

merous, but slightly larger (Photo 2b). The nuclei of

stage III oocytes are located peripherally (near the

cell membrane), and there are single, large lipid

drops (Photo 2c). Cells with no nuclei are classified

as stage IV, and in these oocytes germinal vesicle

breakdown (GVBD) has begun (Photo 2d; Zak and

Szczepkowski 2004). While the sex cells are being

sampled, the fish should be anesthetized. Pikeperch

can be anesthetized using etomidate (Propiscin, IFI,

Olsztyn; Kazu and Siwicki 2001) in doses of 1.0-2.0

cm3 dm-3 (Demska-Zak and Zak 2002).

The application of in vivo methods for determin-

ing the maturity stage of pikeperch oocytes allows

making an initial estimation of the degree to which the

fish are ready to spawn (i.e., before applying hormonal

stimulation and stocking spawners into cages), ob-

serving the progress of maturation in individual fe-

males, and predicting the time of spawning

(Demska-Zak and Zak 2002). It also permits

achieving significant improvement in the effectiveness

of reproduction conducted in cages (Zak and


(a) (b)

(c) (d)

Photo 2. Maturity stage of pikeperch oocytes: (a) stage I (nucleus in the center of the cell, dissipated lipid drops); (b) stage II ( nucleusmigration, lipid occurs in several larger drops); (c) stage III (nucleus shifted beyond radiant field of egg cell, lipid drop in one ball); (d) stage IV (disintegration of the morphological nuclear structure (GVBD)) (arrows indicate nucleus position in chosen oocytes).

Demska-Zak 2001). In this study discussed, cubiccages with a volume of 8 m3 fitted with spawning nestsrecommended by Salminen et al. (1992) (surface area0.25 or 0.36 m2). It was noted that hormonal stimula-tion with hCG (400-600 IU kg-1 b.w.) significantly in-creased the percentage of females that spawned. Thenumber or dose of the hormone was not noted to havehad an effect on spawning (percentage of ovulating fe-males or latency time). Tests were performed on theeffects of a single (400 IU hCG kg-1 b.w.) or a double(first dose 200 IU hCG kg-1 b.w., second dose, admin-istered after 24 h, 300-400 IU hCG kg-1 b.w.) dose ofhormone on the effects of reproduction (Zak andDemska-Zak 2001, Zak et al. 2001). Hormonalstimulation increased the percentage of ovulating fe-males most significantly in the group of fish that werethe least mature (oocytes in stage I). In this group,83.4% of the females spawned, while none of the fe-males from the control group did so (placebo of 0.9%NaCl solution administered). Among the females withoocytes in stage II that were stimulated with hCG, thepercentage that ovulated was 96.2% (57.4% morethan in the control group). Hormonal stimulation didnot have such a significant impact on females withoocytes in stage III; however, in comparison to the fe-males from the control group, 20% more females ovu-lated (80.0 vs. 59.6%). Hormonal stimulation wascounter indicated for the most mature females (stageIV oocytes) since all the fish from this group spawnedspontaneously (Demska-Zak and Zak 2002).During two spawning events conducted in theMazurian Lakeland (northern Poland), females withoocytes in stages I, II, III, and IV comprised 36.5, 38.1,22.9, and 2.5%, respectively, of all the females exam-ined. After hormonal stimulation, as many as 87% ofthe females with oocytes in stages I, II, or III spawned,while only 33% of the spawners from the controlgroup were spent (Demska-Zak and Zak 2002).When expressed as the percentage of ovulating fe-males, the results obtained were better than those re-ported by Antila et al. (1988). The reason for thisdiscrepancy could have been different prevailing ther-mal conditions during the tests as well as the particu-lar reaction of the spawners to the hormones applied.

Demska-Zak and Zak (2002) not only noteda greater percentage of ovulating females, but theyalso noted a shortened latency time and synchroniza-tion in spawning, which is contrary to the findings re-ported by Antila et al. (1988). The latency time amongfemales with oocytes in stages II or III that were sub-jected to hormonal stimulation was 3.6 and 1.7 days,respectively, while in the control group it was 5.4 and2.8 days, respectively. The lack of progress in matura-tion among the females with the least mature oocyteswhich were not stimulated hormonally is puzzling. Af-ter 6 to 9 days of holding the fish in the cages, onlyslight progress was noted in the maturation of theoocytes. In the samples collected, the majority of eggswere still in stage I (50-70%), while in 30-50% of theoocytes the beginning of nuclear migration was noted(stage II). It is possible that this resulted from thestress stemming from capture, transport, and manipu-lation. The processes of oocyte maturation and ovula-tion can be halted as a consequence of physiologicalreactions that occur in females subjected to stress(Schreck et al. 2001). Heightened levels of cortisol,a hormone released as a reaction to stress, might havean impact on the functioning of the hypothala-mus-pituitary-gonadal axis (HPGA), which leads todisturbances in the maturation of oocytes and ovula-tion (Carragher et al. 1989). The application of hCGhormonal stimulation had a clearly therapeutic effectthat led to increased systemic levels of gonadotropinand the release of regulatory mechanisms.

Spawners death are often noted within the firstfive days that the fish are held in cages during thistype of reproduction. It was also confirmed thatlosses among the fish that are stimulated with hor-mones are higher than in the control group (Antila etal. 1988). Zak and Demska-Zak (2001) andDemska-Zak and Zak (2002) did not note thisnegative phenomenon in either the control groups orthose stimulated hormonally. Losses throughoutspawning (8-13 days) reached 1-2% of all the fish.Symptoms of fungal infection were observed espe-cially in the less mature females. It must be notedthat the fish were manipulated after having been an-esthetized, which could have had a advantageous im-pact on their condition.


Variable atmospheric conditions (especiallylower temperatures that occurred, known as Maycooling), that are often observed during the naturalpikeperch spawning period (review in Lappalainen etal. 2003) can influence the course of spawning mi-grations and natural spawning, as well as the effec-tiveness and timing of cage spawning. If there aredrastic decreases in water temperature, pikeperchcan discontinue spawning, and if these conditionshold, the females can even reabsorb their oocytes(Golovanenko et al. 1970). Salminen et al. (1992)confirmed that when pikeperch cage spawning wasconducted during a year when average springweather conditions prevailed, the females depositedtheir eggs within a period of 5.9 to 13.1 days. Duringcolder spring weather, the pikeperch needed as manyas 40 days to spawn. Demska-Zak and Zak(2002) conducted cage spawning in two years withsignificantly different thermal conditions. During thefirst year, the mean water temperature was 10.0C(range of 8.1-15.6C), and in the second year themean was 16.2C (range 13.8-18.1C). The lowerwater temperature resulted in a spawning period thatwas five days longer (eggs obtained for 13 days). Theeffectiveness of spawning at the two water tempera-tures expressed as the percentage of females that de-posited eggs, their working fecundity, and thepercentage of eggs survival to the eyed-egg stage wassimilar. It should be emphasized that in the colderyear, the females deposited eggs even at tempera-tures lower than 10.0C (i.e., 8.0C). Thus, it wouldappear that females which had already attained theappropriate maturation stage spawned despite thesignificantly lowered water temperature (Zak2009). In less mature individuals, it is necessary toapply hormonal stimulation (Demska-Zak andZak 2002). Holding fish in cages for long periodswhen lower temperatures prevail can have a negativeimpact on the condition and health of the fish thuslowering the effectiveness of this method.

Artificial spawning of wild pikeperch

Most of the pikeperch spawners used in artificial re-production are wild specimens obtained from natu-ral water bodies, although cultivated spawners heldin earthen ponds are sometimes used (Horvth et al.1984, Schlumberger and Proteau 1996, Steffens etal. 1996, Zak and Demska-Zak 2005, Zak2009). Spawners from natural waters are caught infall (October-November) or in spring (March-May),during spawning migrations (Zak 2009). The fishcaught in fall are held for the winter in earthenponds. Pikeperch feed rather intensively during thewinter, so it is important to ensure that an appropri-ate food base is available. The minimum monthlyfeed fish biomass should be 20% of the pikeperchspawner biomass (Horvth et al. 1984, Wojda 2006).This species prefers feeding on small-sized fish, thusthe body weight of the prey fish should not exceed8-10% of the spawner body weight (Steffens et al.1996, Szczepkowski and Zak 2003).

It is very important to ensure that the spawnersare transported under appropriate conditions. It isalso recommended to use some sort of anti-stressagent such as sodium chloride (3-5 g NaCl dm-3) oretomidate (0.02-0.05 cm3 dm-3; Schlumberger andProteau 1996, Zak and Demska-Zak 2005,Zak 2009).

Applying thermal and hormonal stimulation is pos-sible if reproduction is conducted in a hatchery equippedwith a RAS. As a rule, males do not require hormonalstimulation (Zak and Demska-Zak 2005, Rnyai2007). However, if they are not ripe when they are deliv-ered to the hatchery, they should be stimulatedhormonally with half the dose given to the females(Steffens et al. 1996). Mainly gonadotropins are used inthe hormonal stimulation of pikeperch (CPE and hCG;Antalfi 1979, Steffens et al. 1996, Zak andDemska-Zak 2005, 2006, Wang et al. 2009). Effectivedosages of these preparations range from 2.4 to 5.0 mgCPE kg-1 b.w. and 100-700 IU hCG kg-1 b.w. (Table 1).The hormonal preparations are administered in eitherone or two doses. The period between injections is usu-ally 24 hours, although Steffens et al. (1996)


recommend a 12-hour interval between injections ofCPE. These authors also recommend administering thetotal hCG dose in three to five injections. Zak andDemska-Zak (2005), however, did not note that thenumber of injections or the sizes of the hCG doses (400or 700 IU kg-1 b.w.; administered in two portions) hadany effect on the effects of reproduction (Table 1). Thesize of the doses and the number of injections should bedetermined based on the maturity of the females (Rnyai2007, Zak 2009). Females with oocytes in stage I canbe stimulated twice, but for those with oocytes in stagesII or III (Photo 2) it is sufficient to use one injection (i.e.,200 IU hCG kg-1 b.w.; Zak and Demska-Zak 2005,2006). Either etomidate (1.0-2.0 cm3 dm-3, Zak andDemska-Zak 2005) or phenoxyethanol (0.1-0.3 cm3

dm-3; Schlumberger and Proteau 1996, Wang et al.2009) can be used to anesthetize the fish prior to manip-ulation (collecting oocyte samples, injections).

Studies have been conducted of the effects ofother gonadotropins on the maturation of oocytesand ovulation in pikeperch including pregnant mareserum gonadotropin (PMSG) (Zak andDemska-Zak 2006). It should be emphasized thatstudies of stimulating fish reproduction with PMSGare not numerous (Brzuska and Ryszka 1990,Bieniarz and Epler 1991). The dose of PMSG appliedwas the same as that of hCG (i.e., 200 IU kg-1 b.w.).While stimulation with hCG produced significantprogress in oocyte maturation 48 h following injec-tion, progress in the group stimulated with PMSGwas only slight (Zak and Demska-Zak 2006).Not until the second injection of PMSG (200 IU kg-1

b.w.) was there a significant stimulatory effect. Theapplication of PMSG resulted in a lengthened latencyperiod and a lowered degree of spawning synchroni-zation (Table 1), but eggs was obtained from all fe-males, and, more importantly, the weight of the eggsexpressed as a percentage of female body weight wassignificantly higher in the PMSG group than in thehCG group (15.9 and 10.4% b.w., respectively). Thegonadotropins administered were not observed to ef-fect the quality of the eggs (Zak and Demska-Zak2006). It is possible that a higher dose of PMSGwould likely lead to synchronized spawning. Brzuskaand Ryszka (1990) reported, however, that with carp

even doses of PMSG as high as 2000 IU kg-1 b.w. didnot have a significant effect on the oocyte maturationprocess or on ovulation. These authors also notedthat fish stimulated with PMSG first and then CPE,matured earlier than those injected exclusively withCPE. It was also confirmed that the carp stimulatedwith both PMSG and CPE produced a greateramount of eggs.

Currently, domestic animals are stimulated to re-produce using a hormonal preparation comprisingboth hCG and PMSG. Initial studies indicate that us-ing this preparation in pikeperch production is notfully justified because of the higher cost and the factthat it does not produce a greater percentage of ovu-lating females. Additionally, as was the case with us-ing PMSG exclusively, the latency time is relativelylong and the degree of spawning synchronization nothigh (Zak et al., unpublished data).

Gonadoliberins are used less frequently to stim-ulate the artificial spawning of wild pikeperch, andthe available literature indicates that it is more com-mon to use GnRHa (D-Ala6 desGly10-mGnRH) andOvopel (Schlumberger and Proteau 1996, Zak andDemska-Zak 2005; Table 1). The effects of stimu-lating pikeperch with GnRHa are satisfactory(Schlumberger and Proteau 1996), but the resultsachieved with Ovopel are not conclusive. Zak andDemska-Zak (2005) noted that this preparationhad a negative impact on pikeperch reproduction. Incomparison to the females stimulated with hCG, thepercentage of those who deposited eggs was lowerwhen Ovopel was the stimulant. Additionally,spawner mortality increased and the quality of theeggs was poorer (Table 1). Similarly, high mortalitywas noted in wild ide, Leuciscus idus (L.), that hadbeen stimulated with Ovopel (Kucharczyk et al.1999). It must be emphasized that Ovopel is usedsuccessfully in the reproduction of cyprinids and cat-fishes (i.e., Horvth et al. 1997, Brzuska andGrzywaczewski 1999, Brzuska 2003, 2004). Itshould be noted that the fish material used in thecited studies were highly domesticated (in ponds)making them more resistant to all kinds of manipula-tion and the stress associated with it.



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arat

ion

Dos

e(p

erkg

body

wei

ght(

b.w

.))Ad

min

istra

tion

ofdo

sesa

ndtim

ein

terv

albe

twee

n

inje

ctio

ns

Wat

er

tem

pera

ture

(C)

Late

ncy

time

(h)(1

)O

vula

tion

(%)

Surv

ival

(%)

Auth

or

CPE

3.0-

5.0

mg

2do

ses(

10an

d90

%),

24h

14.0

2880

80-9

5An

talfi

(197

9)

2.4

mg

2do

ses(

0.8

and

1.6

mg

kg-1

b.w

.),24

h12

.0-1

5.5

28-3

575

75(2

)Za

ke

tal.,

unpu

blish

edda

ta

4.0

mg

2do

ses(

1.0

and

3.0

mg

kg-1

b.w

.),24

h15

.5-1

6.5

24-3

890

>95

Rny

ai(2

007)

hCG

100-

200

IUn.

d.19

.0-2

0.0

10n.

d.n.

d.St

effe

nset

al.(

1996

)

700

IU2

dose

s(20

0an

d50

0IU

kg-1

b.w

.),24

h12

.0-1

5.5

20-2

870

79(2

)Za

ke

tal.,

unpu

blish

edda

ta

200

IU1

dose

10.0

-15.

824

-70

100

73(2

)Za

ka

ndD

emsk

a-Za

k(

2006

)

400

IU2

dose

s(20

0an

d20

0IU

kg-1

b.w

.),24

h10

.2-1

5.5

22-3

283

72(2

)Za

ka

ndD

emsk

a-Za

k(

2005

)

700

IU2

dose

s(20

0an

d50

0IU

kg-1

b.w

.),24

h10

.2-1

5.5

25-3

610

068

(2)

PMSG

400

IU2

dose

s(20

0an

d20

0IU

kg-1

b.w

.),48

h10

.0-1

5.8

48-9

610

076

(2)

Zak

and

Dem

ska-

Zak

(20

06)

GnR

Ha

100

g+

pim

ozid

e10

mg

n.d.

14.0

-20.

025

-30

n.d.

>80

Schl

umbe

rger

and

Prot

eau

(199

6)

Ovo

pel(3

)0.

75pe

llet

2do

ses(

0.25

and

0.50

pelle

tkg-

1b.

w.),

24h

10.2

-15.

5-

0-

Zak

and

Dem

ska-

Zak

(20

05)

1.25

pelle

t2

dose

s(0.

25an

d1.

00pe

lletk

g-1

b.w

.),24

h10

.2-1

2.5

42-6

250

3(2)

No

stim

ulat

ion

0.5

ml0

.7%

NaC

l2

dose

s(0.

2an

d0.

3m

lkg-

1b.

w.),

24h

12.0

-15.

535

-72

2582

(2)

Zak

eta

l.,un

publ

ished

data

0.7

ml0

.7%

NaC

l2

dose

s(0.

2an

d0.

5m

lkg-

1b.

w.),

24h

10.2

-15.

052

-99

5070

(2)

Zak

and

Dem

ska-

Zak

(20

05)

(1)ti

me

mea

sure

dfr

omla

stho

rmon

edo

se;(

2)su

rviv

alde

term

ined

atth

eey

ed-e

ggst

age;

(3)1

pelle

tofa

nav

erag

ew

eigh

tof2

5m

gco

ntai

ns18

-20

gD

-Ala

6P

ro9 N

Et-

mG

nRH

and

8-10

mg

met

oclo

pram

ide)

;n.d

.no

data

Hodson and Sullivan (1993) recommend usinggonadotropin instead of gonadoliberin when repro-ducing wild fish. They conformed in a study on wildbass, Morone saxatilis (Walb.), that stimulating withhCG, a hormone that acts directly on the gonads, hada more positive impact on the maturation of oocytes,ovulation, and spermiation than did GnRH. The higheffectiveness of this hormone for stimulating andsynchronizing reproduction is explained by the rela-tively long half-life of hCG in the bloodstream (Ohtaand Tanaka 1997). Gonadoliberins act at the higherlevel of the HPG axis, which is why the latency periodis usually longer than after the application of gonado-tropin. It cannot be ruled out that the longer latencyperiod and accompanying stress might be the causeof the high mortality among wild spawners (Zoharand Mylonas 2001).

Currently, two methods for reproducingpikeperch are used at hatcheries: the tank methodand artificial spawning. In the first, after hormonalstimulation, a set of spawners (1 + 1-2 ) is placedin a tank on the bottom of which is a spawning nest(these fish spawn on a substrate; Horvth et al. 1984,Schlumberger and Proteau 1996, Steffens et al.1996, Rnyai 2007, Wang et al. 2009, Zak 2009).After injecting the fish with the hormonal stimulant,it is recommended to conduct thermal stimulation.Steffens et al. (1996) recommend increasing watertemperature to 19-20C, while other authors recom-mend temperatures from 10-12 and 14-16C(Antalfi 1979, Zak 2009). This method reduces thenumber of manipulations the spawners are subjectedto during the process of obtaining sex products, butquite frequently a portion of the eggs are depositedoutside of the spawning nests. The eggs can also bedeposited in a thick layer, which promotes the devel-opment of Saprolegnia sp., and consequently re-duces the effects of spawning (Zak 2009). It wouldappear that the optimal solution is to conduct artifi-cial reproduction. Pikeperch eggs obtained artifi-cially are fertilized with milt collected from maleswith syringes (Steffens et al. 1996, Zak andDemska-Zak 2005). Pikeperch have thick semenwith sperm concentrations that range from 16 to 20million cm-3 of semen (mean 19.8 million cm-3;

Zak and Demska-Zak 2005). To fertilize 100 g ofeggs it is recommended to use 1.0-2.0 cm3 semen(Steffens et al. 1996, Zak and Demska-Zak2005). Sperm motility usually ranges from 50 to90%, which is why it is recommended to fertilize anygiven portion of eggs with the milt taken from 2 to 3males (Zak and Demska-Zak 2005).

Adhesiveness can be removed from the eggs bybathing it in a talc-sodium chloride solution (100 gsalt + 25 g talc + 10 dm3 water) for 45 to 60 min(Schlumpberger and Schmidt 1980). The disadvan-tage of this method is that it is time and labor inten-sive. Removing adhesiveness with a tannin solutionis much faster and can be done at a solution concen-tration of 0.5-1.0 g dm-3 of water for a period of 5 min(Demska-Zak et al. 2005). Pikeperch eggs can alsobe cleared of adhesiveness with an aquatic solutionof protease (recommended concentration of 0.5%(5 cm3 dm-3 water; length of procedure 2 min;Zak et al. 2006). The eggs are incubated in stan-dard Weiss jars at a recommended water tempera-ture of 16.0 to 17.0C (Steffens et al. 1996).Kokurewicz (1969) reported, however, that the bestlarval development and longest body length is ob-tained when the eggs are incubated at a water tem-perature of 12.0-16.0C. Jars of a volume of 7 dm3

can accommodate from 0.5 to 5.0 dm3 of eggs. Therecommended water flow rate is 0.5 dm3 min-1 at thebeginning of egg incubation and 4.0-5.0 dm3 min-1

in later periods (Steffens et al. 1996). During incuba-tion, prophylactic baths to prevent the developmentof fungi can be used (i.e., 100 ppm of formalin for 5min; Rnyai 2007). Based on data available in the lit-erature, Lappalainen et al. (2003) that the pikeperchegg incubation period (from fertilization to hatchinglarvae) can be calculated with the following formu-lae: DD = 1255 T-1.07 or I = 30124 T-2.07,where: DD incubation time (D), I incubation time(h), T water temperature (C).

When catching spawners prior to the spawningseason, it should be borne in mind that malepikeperch generally mature earlier and reach thespawning grounds earlier (Salminen et al. 1992,Lappalainen et al. 2003). In the initial stages ofcatching spawners, it is usually only possible to


obtain males, which then have to be held for severaldays to even two to three weeks until mature femalespawners are caught. An alternative solution, that isless costly than holding the males, is to strip them ofmilt and store it under the appropriate conditions. Todate, studies of short-term storage of semen havebeen conducted mainly on salmonids (Stoss 1983,McNiven et al. 1993) and cyprinids (Ravinder et al.1997, Glogowski et al. 2008). Moore (1987) devel-oped a method for the short-term storage of the se-men of walleye, Sander vitreus (Mitch.).Demska-Zak and Zak (2003) confirmed that un-diluted pikeperch semen held under refrigeration(+4C) in an oxygen atmosphere remains viable forup to 12 days. Using diluting agents, such as thoseused for the storage of semen from other fish species(i.e., Cortland and Moore fluids; Brown and Moore1996) did not improve the biological quality of thesemen. What determines how long pikeperch spermremains viable is the maintenance of appropriate ox-ygen conditions (daily oxygen exchange) in the con-tainer in which the semen is stored. Pikeperch miltstored in open containers at a temperature of + 4Cwas viable for just a day (Demska-Zak and Zak2003). The positive effects of oxygen on semen qual-ity was also observed in salmonid fish (Stoss andHoltz 1983). It is noteworthy, however, that not allfish species exhibit this same dependency(Glogowski et al. 2008). A high percentage of fertil-ized eggs (80-90%) can be obtained when sperm mo-tility does not fall below 50% (Brown and Moore1996). Such viability was confirmed in pikeperchsperm up to 7 days after semen collection(Demska-Zak and Zak 2003). Bokor et al. (2007)reported promising results using cryopreservedsperm to fertilize the eggs of this species. They alsoconfirmed that good effects are guaranteed by usingmethanol (MeOH) or dimethyl sulfoxide (DMSO) ascryoprotectants. When cryopreserved pikeperch miltwas used, in excess of 40% of the eggs were fertilized.These same authors suggested that contaminationwith urine appears to be the key obstacle to overcomewhen developing more effective methods for thecryopreservation of the semen of this species.

Out-of-season pikeperch reproduction

Some of the most recent studies of pikeperch are fo-cused on out-of-season spawning of this species. Thefirst documented reproduction of pikeperch prior tothe natural spawning season were performed by Zakand Szczepkowski (2004). Currently, this method isalso being used to reproduce wild pikeperch (Zakand Szczepkowski 2004, Zak et al. 2005, Rnyai2007), as well as cultivated pikeperch reared in RAS(Zak 2007). The process of intense yolk accumula-tion (exogenic vitellogenesis) begins as early as in lateOctober and early November (ovary maturation stageIV; Sakun and Bucka 1968). During the subsequent5-6 months the oocytes achieve their full size and fol-lowing a relatively short maturation period they areready to be deposited during spawning (ovulation). Itwas confirmed that subjecting pikeperch tophotothermal stimulation shortens the duration ofvitellogenesis and reproduction can be achieved sev-eral months prior to the natural spawning season(Zak and Szczepkowski 2004, Rnyai 2007). Thefull thermal cycle of stimulation for spring spawningfish comprises three phases: cooling phase (CP), chill-ing phase (CHP), and warming phase (WP) (Migaud etal. 2002). Zak and Szczepkowski (2004) applieda 16-week thermal stimulation cycle (CP 6 weeks;CHP 6 weeks; WP 4 weeks). This resulted in ob-taining eggs 3-4 months prior to the natural spawningseason of this species. The length of the full thermalstimulation cycle for pikeperch is significantly shorterthan that for perch, Perca fluviatilis L. Migaud et al.(2002) noted that with this species the duration ofCHP, which should last about 5 months, is significant.Rnyai (2007) suggests that with pikeperch a coolingperiod of 3 months is sufficient. In turn, Zak (2007)concluded that the duration of the CHP might beshortened to 6 weeks (temperature 8.0C) or 8-9weeks (temperature 10.0C). Similar solutions arealso recommended by Mller-Belecke and Zienert(2008).

There are several ways of performing thermalstimulation. In variant I, the fish undergo CP undernatural conditions (ponds or lakes). Spawners are


caught in fall and placed in a hatchery under fully con-trolled conditions, where they are subjected to the twofinal phases of stimulation (CHP + WP). In variant II,the fish are stocked into ponds and then removed dur-ing winter. This allows conducting the first two phases(CP + CHP) under natural conditions. Only WP isconducted under controlled conditions. In variant III,all three phases of thermal stimulation are conductedunder fully controlled conditions (Zak et al. 2005).Rnyai (2007) applied the second method success-fully, while Zak and Szczepkowski (2004) andZak (2007) obtained good results with variant III.Rnyai (2007) caught subsequent batches of spawn-ers in the ponds from January to May, and concludedthat the fish that had been held in ponds during thefall and winter for phases CP and CHP required justa 7-day period of increased temperature (WP) afterbeing moved to the hatchery. The extension of thisphase (14 days) did not improve the results of spawn-ing (Rnyai 2007). During WP, the water temperatureis generally increased to 15-16C (Rnyai 2007, Zak2007; Table 2), at a maximum daily temperature in-crease of 2C (Rnyai 2007, Mller-Belecke andZienert 2008). Rnyai (2007) observed that applyinghigher temperatures (18C) shortened the latencytime, but it did not affect the percentages of ovulatingfemales or fertilized eggs. The latency time was also af-fected by the period when the fish were caught in theponds and moved to the hatchery. From January toApril, this period was shortened significantly by 120to 60 h, respectively (Rnyai 2007). One of the advan-tages of variants I and II is that the thermal stimulationis accompanied by the natural photoperiod. One solu-tion that permits exploiting the natural photoperiod isto place the fish in recirculating systems (controlledtemperature) located in glasshouses (Zak andSzczepkowski 2004). In the studies cited above, ashifted photoperiod was only applied during WP.Over a month, along with increasing water tempera-ture, the photoperiod was also changed graduallyfrom 8:16 to 14:10 L:D (Zak and Szczepkowski2004, Zak 2007). The stimulatory effect ofphotoperiod on percid fish is not unequivocal(Malison et al. 1998, Migaud et al. 2002, Rnyai2007). Kayes and Calbert (1979) noted that yellow

perch, Perca flavescens (Mitch.), held under variousphotoperiod regimes (L:D; 13.5:10.5; 10.5:13.5;6:18; 18:6) spawned at similar times. Rnyai (2007)concluded that even the application of thephotoperiods of L:D; 12:12 and 0:24 did not influencethe out-of-season spawning of pikeperch. Dabrowskiet al. (1994) and Migaud et al. (2002) suggest thatwith percids that reproduce in spring, such as yellowperch and European perch, photoperiod does not haveas significant an effect on the process ofgametogenesis, as does water temperature.

In addition to photothermal stimulation, one of theconditions for achieving full oocyte maturation,spermiation, and ovulation in out-of-season pikeperchreproduction was to apply hormonal injections (Zakand Szczepkowski 2004). In the fish from the controlgroup, which were injected with a placebo and sub-jected only to environmental stimulation, no progresswas noted in the maturation of oocytes (Zak andSzczepkowski 2004, Rnyai 2007, Zak 2007).Malison et al. (1998) reached similar conclusions instudies of out-of-season spawning of walleye. Goodpikeperch reproduction results can be anticipatedwhen hCG and CPE are administered either separatelyor in combination (Table 2). In out-of-season reproduc-tion males are not as mature as wild individuals caughtin the pre-spawning period, which is why it is necessaryto conduct hormonal stimulation (i.e., 200 IU hCG kg-1

b.w.; Zak 2007). The number of doses of this hor-mone (1-3 doses) administered was not noted to haveaffected either the latency time or the biological qualityof the sex products (Zak and Szczepkowski 2004).Likewise, the dose of hormone (200 and 400 IU hCGkg-1 b.w.) or the age of cultivated pikeperch females(2+ and 3+) were not noted to have influenced the la-tency period or the working fecundity (Zak 2007).When CPE or a combined injection of CPE and hCGare applied, it is recommended to use two doses(Rnyai 2007). Three injections of CPE do not signifi-cantly improve the effects of spawning in comparisonwith females that were injected twice with CPE. How-ever, with fish that do not spawn within 5-6 days, theapplication of a third injection might be effective (i.e., 3mg CPE kg-1 b.w.; Rnyai, 2007). The shortest latencytime is guaranteed with two injections (first dose of



Tab

le2

Impa

ctof

vari

ous

horm

onal

prep

arat

ions

onth

eef

fect

sof

out-

of-s

easo

npi

kepe

rch

repr

odu

ctio

n(h

CG

hu

man

chor

ioni

cgo

nado

trop

in;C

PE

ca

rppi

tuit

ary

extr

act;

Ovu

relin

G

nRH

anal

ogu

e(R

nya

i200

7);m

tc

met

oclo

pram

ide;

Ovo

pel

mam

mal

ian

GnR

Han

alog

ue

wit

ha

dopa

min

ein

hibi

tor

(see

Tab

le1)

(ran

geor

mea

nva

lues

SD

)

Hor

mon

e/pr

epar

atio

nD

ose

(per

kgbo

dyw

eigh

t(b.

w.))

Adm

inist

ratio

nof

dose

s,tim

ein

terv

albe

twee

nin

ject

ions

,ch

arac

teris

ticof

fish

Wat

erte

mpe

ratu

re(

C)La

tenc

ytim

e(h

)(1)

Ovu

latio

n(%

)Su

rviv

al(%

)Au

thor

hCG

200

IU1

dose

12.0

-15.

566

7

100

77.5

5.

6(4)

Zak

and

Szcz

epko

wsk

i(20

04)

400

IU2

dose

s(20

0an

d20

0IU

kg-1

b.w

.),24

h12

.0-1

5.5

71

910

073

.0

8.9(

4)

600

IU3

dose

s(20

0,20

0,20

0IU

kg-1

b.w

.),24

h12

.0-1

5.5

70

510

071

.5

9.1(

4)

200

IU1

dose

,cul

tivat

edsp

awne

rs,a

ge2+

12.0

-16.

010

1

1380

61.0

14

.8(4

)Za

k(

2007

)

200

IU1

dose

,cul

tivat

edsp

awne

rs,a

ge3+

12.0

-16.

088

14

9370

.7

10.2

(4)

400

IU1

dose

,cul

tivat

edsp

awne

rs,a

ge2+

12.0

-16.

098

13

100

64.0

20

.7(4

)

400

IU1

dose

,cul

tivat

edsp

awne

rs,a

ge3+

12.0

-16.

099

7

100

73.3

11

.3(4

)

400

IU2

dose

s(20

0an

d20

0IU

kg-1

b.w

.),24

h(2)

15.5

-16.

576

6

100

87

8(5)

Rny

ai(2

007)

hCG

+CP

E20

0IU

+3

mg

first

dose

hCG

,sec

ond

dose

CPE,

24h(

2)15

.5-1

6.5

108

23

7585

10

(5)

200

IU+

3m

gfir

stdo

sehC

G,s

econ

ddo

seCP

E,24

h(3)

15.5

-16.

512

0

450

>95

(5)

hCG

+CP

E20

0IU

+3

mg

first

dose

hCG

,sec

ond

dose

CPE,

24h(

2)15

.5-1

6.5

67

310

087

6(

5)

CPE

6m

g2

dose

s(3

and

3m

gkg

-1b.

w.),

24h(

2)15

.5-1

6.5

119

23

7575

23

(5)

6m

g2

dose

s(3

and

3m

gkg

-1b.

w.),

24h(

3)15

.5-1

6.5

115

25>

95(5

)

6m

g2

dose

s(3

and

3m

gkg

-1b.

w.),

24h(

2)15

.5-1

6.5

71

510

091

6(

5)

6m

g2

dose

s(3

and

3m

gkg

-1b.

w.),

24h(

3)15

.5-1

6.5

74

610

088

13

(5)

CPE

+hC

G3

mg

+20

0IU

first

dose

1.5

mg

CPE

kg-1

b.w

.+10

0IU

hCG

kg-1

b.w

.,se

cond

dose

1.5

mg

CPE

kg-1

b.w

.+10

0IU

hCG

kg-1

b.w

.,24

h(2)

15.5

-16.

578

8

100

90

12(5

)

Ovu

relin

20g

first

dose

5g

kg-1

b.w

.,se

cond

dose

15g

kg-1

b.w

.,24

h15

.5-1

6.5

86

910

043

34

(5)

Ovu

relin

+m

tc20

g+

10m

gm

tcfir

stdo

se5

gkg

-1b.

w.+

10m

gm

tc.s

econ

ddo

se15

gkg

-1b.

w.,

24h

15.5

-16.

593

38

5056

22

(5)

Ovo

pel

0.2

pelle

t2

dose

s(0.

1an

d0.

1pel

letk

g-1

b.w

.),24

h15

.5-1

6.5

78

110

054

43

(5)

(1)ti

me

mea

sure

dfr

omad

min

istr

atio

nof

first

horm

one

dose

;(2)

fish

cau

ghtf

rom

pond

san

dhe

ldat

spaw

ning

tem

pera

ture

for7

days

prio

rto

inje

ctio

n;(3

)fis

hca

ugh

tfro

mpo

nds

and

held

atsp

awni

ngte

mpe

ratu

refo

r14

days

befo

rein

ject

ion;

(4)su

rviv

alde

term

ined

atth

eey

ed-e

ggst

age;

(5)su

rviv

alde

term

ined

16-1

8h

afte

rfe

rtili

zati

on

hCG, second dose of CPE; Rnyai, 2007). Results todate also indicate that in out-of-season reproduction,stimulation with GnRH preparations (i.e., Ovopel andOvurelin (D-Phe6-mGnRH); Rnyai 2007) produceworse results than GtH (longer latency period and/orlower percentage of fertilized eggs; Table 2).Gonadoliberins, and in particular their super active an-alogues (GnRHa), potentially have properties that couldrender them more advantageous than GtH for the mat-uration of gametes, for example, by influencing the syn-thesis and excretion of somatropins, tyreotropins, andprolactin. However, the excretion of GtH after the appli-cation of GnRH might be inhibited by dopamine (Zoharand Mylonas 2001). This is why GnRH is administeredalong with dopamine blockers (Zohar and Mylonas2001). Rnyai (2007) did not note more positive effectswhen metoclopramide was administered along withGnRH (Ovurelin) to stimulate pikeperch spawning.Kouril et al. (1997) also failed to note a more advanta-geous effect on the spawning of European perch whenGnRH was administered along with a dopamineblocker.

Hormonal stimulation procedures should bepreceded by determining the stage of maturity of thefemales. It is recommended to use the same in vivomethod for doing this as was used in cage reproduc-tion and in artificial reproduction in the naturalspawning period for this species (Zak andSzczepkowski 2004, Mller-Belecke and Zienert2008). Additionally, it was confirmed that changes inbody weight observed in hormonally stimulated cul-tivated female pikeperch corresponded to gonadalmaturity degree. This might be a valuable aid in de-termining their stage of maturity, as well as predict-ing the period in which eggs will be obtained (Zak2007).

One of the problems encountered inout-of-season reproduction is the high incidence ofpost-spawning mortality of spawners. Rnyai (2007)confirmed that all of the females that had beenstripped artificially died within five days of obtainingeggs. Mortality among fish that spawned in tanks(eggs deposited on substrate) was also high at about60%. The cause of such high losses might have ma-nipulation stress. The origin of the fish is also

significant. The material used in Rnyais (2007) re-production study were wild fish, which are decidedlymore susceptible to stress than are cultivated fish.When conducting artificial reproduction ofpikeperch that have been reared from larvae in RASon commercial feed, post-spawning losses are nothigh and do not exceed 10% (Zak 2007). The samefemales held in RAS can reproduce for the subse-quent three or four seasons without any negative im-pact on the quality of the eggs obtained (Zak et al.,unpublished data).

Doubtlessly, catching, transporting, and manip-ulating fish during the spawning season leads tohigher losses. This is especially true when inappro-priate methods are applied (Zak 2009). One solu-tion that would minimize fish manipulation would beto subject them only to photothermal stimulation.The photothermal stimulation procedures presentedabove do not prepare pikeperch for spawning with-out the application of hormonal stimulation (Zakand Szczepkowski 2004, Rnyai 2007, Zak 2007).However, Mller-Belecke and Zienert (2008) appliedphotothermal stimulation, following which the ma-jority of fish (91% of the females) held in the tanksspawned (eggs were deposited in nests). After initial,year-long rearing in RAS (temperature 22-24C), thepikeperch were moved to lake cages, where theirrearing continued. It was confirmed that the applica-tion of a chilling phase of 43 to 60 days (CHP wasconducted in lake cages; temperature 10.0C), fol-lowed by a warming phase of 44 to 68 days (watertemperature approximately 15C; photoperiod L:D16:8; fish held in RAS) allowed obtaining fertilizedeggs two months prior to the natural spawning period(Mller-Belecke and Zienert 2008). Using this proce-dure decreased post-spawning losses, which were12.5% for the females. The mean weight of the eggsobtained in various experimental groups rangedfrom 9.8 to 24% b.w., and in most instances, thesewere higher than that obtained during artificial,out-of-season, hormonally-stimulated reproductionof this species (Rnyai 2007, Zak 2007). It wassymptomatic that photothermal stimulation wasmore effective among females than among males(Mller-Belecke and Zienert 2008). These authors


put forth the hypothesis that perhaps holding fe-males and males in the same tanks (especially duringWP) would have a more advantageous impact ontheir maturation (potential effect of pheromones andvisual stimulation).

Final comments, research priorities

Knowledge pertaining to pikeperch reproduction hasbeen increased substantially, especially in recentyears. Methods for pikeperch reproduction in lakecages have been improved, and the application of invivo methods for determining the oocyte maturitystage and hormonal stimulation (especially in lessmature females) have permitted increasing the effec-tiveness of cage spawning and the artificial reproduc-tion of wild fish. Preparations containing GtH (CPEand hCG) have proved to be particularly effective.The application of CPE carries the risk of transmit-ting diseases borne by the fish from which the pitu-itary extract is obtained. Another disadvantage ofCPE is that is is often a non-standard product, andother hormones contained in the pituitary can haveside effects. After the application of GtH, which areproteins, and particularly after the administration ofhCG, it is possible for the immune system to produceanti-bodies (Zohar and Mylonas 2001). Conse-quently, when using hCG in subsequent reproduc-tive seasons, it might be necessary to use increasinglyhigher doses of the preparation. No such reactionwas noted among the pikeperch spawners that werestimulated with hCG in three to four subsequentspawning seasons (Zak et al., unpublished data). Itcannot be ruled out, however, that this type of prob-lem will arise in the subsequent stages of the domes-tication of this species. Bearing in mind theeffectiveness of this preparation, its standardization,the ease with which it can be prepared, the smalldose required, its low cost, as well as the repeatabilityof the results achieved, hCG can be recommendedfor use in pikeperch reproduction. Because of the po-tentially positive factors of GnRH, it is highly recom-mended that further studies be conducted to develop

optimal methods for stimulating pikeperch repro-duction with this type of preparation (Rnyai 2007).As the importance of so-called organic aquacultureincreases, undoubtedly so too will the role of meth-ods for reproducing pikeperch that are based on onlyon photothermal stimulation (Mller-Belecke andZienert 2008).

The negative influence of intense rearing condi-tions and domestication on fish reproduction is notedrelatively frequently (Brooks et al. 1997). The growthof intense pikeperch cultivation will depend on thedevelopment of effective reproduction techniques forcultivated pikeperch spawners held in RAS, and feddiets of commercial feed. Initial studies have con-firmed that this type of reproducer is suitable for arti-ficial spawning (Zak 2007, Mller-Belecke andZienert 2008). However, the priority has to be devel-oping recipes for commercial feeds that meet the nu-tritional needs of the selects and spawners of thisspecies which, in turn, ensures obtaining high qualitysex products and progeny. Studies of fatty acid pro-files have indicated that the eggs of cultivatedpikeperch differs from that of wild pikeperch in thecontents, for example, of polyunsaturated fatty acids(PUFA) (Kowalska et al. 2006). Such differenceswere noted with regard to fatty acids that determinethe quality of eggs and progeny, including, for exam-ple, arachidonic (C 20:4 n-6), eicosapentaenoic(C 20:5 n-3), and docosahexaenoic (C 22:6 n-3)(Izquierdo et al. 2001). Wang et al. (2009) confirmedthat feeding pikeperch commercial feed resulted inlowered artificial reproductive effectiveness in com-parison to that in the group of spawners fed a diet offish. However, the diet of pikeperch spawners wasnot noted to have had an impact on the biologicalquality of the larvae (Wang et al. 2009).

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Streszczenie

Kontrolowany rozrd sandacza Sander lucioperca (L.) artyku przegldowy

W pracy podsumowano najwaniejsze osignicia dotyczcekontrolowanego rozrodu sandacza, jednego z najcenniejszychgospodarczo i ekologicznie europejskich gatunkw ryb sod-kowodnych. Zawarto informacje na temat tara sadzowego,sztucznego tara ryb dzikich (pozyskanych ze rodowiska na-turalnego) i tzw. tara pozasezonowego tego gatunku. Opisanometody i zasady przeprowadzania stymulacji tara fototermi-czej i/lub hormonalnej. Wykazano, e zastosowanie metodyprzyyciowego okrelania stadiw dojrzaoci oocytw (fot. 1i 2) i stymulacji hormonalnej, szczeglnie w przypadku mniejdojrzaych samic, pozwala na istotne zwikszenie

efektywnoci (odsetek owulujcych samic) tara sadzowego isztucznego oraz zsynchronizowanie akcji tarowej. Spordtestowanych do tej pory hormonw i preparatw hormonal-nych (gonadotropiny (GtH), gonadoliberyny (GnRH) i ich syn-tetyczne analogi (GnRHa)), we wszystkich ww. metodachrozrodu sandacza, najbardziej skuteczne okazay si GtH homogenat przysadki mzgowej karpia (CPE) i ludzka gona-dotropina kosmwkowa (hCG) (tabela 1 i 2). Praca zawierarwnie najnowsze informacje na temat krtkoterminowegoprzechowywania nasienia, odklejania i inkubacji ikry sanda-cza.


reproducerea artificiala la salau

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