marine habitat enhancement and urban recreational fishing ......fjshery management in washington....
TRANSCRIPT
Marine Habitat Enhancement andUrban Recreational Fishing in Washington
RAYMOND M BUCKLEY
Introdm·tion
In 1974 the Washington Departmentof Fisheries began a marine fish enhancement program designed to establish marine hahitat enhancement (artificial reefs)and puhlic fishing piers as acr.ept(;d fOtmsof fishery technology for improving urban recreational fishing in the PugetSound region (Fig. J). Both artificial reefsand fishing piers have heen used extensively for many years in some of theAtlantic and Gulf Coast States and inCalifornia to improve recreational fisherycatches and access in previously unproductive fishing locations (Steimle andStone. 1973: Rickards. 19n; Fable andSaloman. 1(74). In contrast. Washington's pier fJshing facilities were limitedto a few access areas on commercedocks. and earlier arlifJcial reef effortswere small-scale projects designed toprovide underwater recreation areas forscuba divers. None of these projects wereprimarily for shore fishing access orurban fishery enhancement.
Recreational fJshing in Pacific North-
ABSFRACT- A marine lish enhanccmentpmgram staned in 1974 has emphasized theuse 0/ habitat enhancement structures (urtilicia/r{:e!'s), hoth in coniunctiun with pu/JIiclishing piers and to create fishing reel~"/orbu(/{ anglers. tn impruve urban recreationalfishing in Puget Sound. Fhl? enhanced areaswere designed and sited to del'elnp hinlogi·calli' into replicates 0/ natural rockv reelcommunities ill order to promote productil'efishNies.
The site selectinn proc"ss was b£lI'ed (In
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west marine waters has been synonymous with fishing for Pacific salmon(Oncorh.l'nchu,\ sp.) from small boats.and this axiom has pervaded from anglers. through fishery managers. to thefunding sources. Consequently. a newprogram directed at enhancement of(.tlier marine fish spt'cies-- using locallyunproven techniques. and partially targeling these fish for an essentially unrecognized clit'ntele--was met initially withfeelings ranging from skepticism to enthusiasm. Fortunately. a significantamount of the enthusiasm to try habitatenhancement and public flshing pierswas generated with the State governmentfunding sources (i.e .. the legislature andthe Interagency Committee for OutdoorRecrC'ation). the fishery clientele. and
Ra)lllund M. Buckley is Chief. Marine Fish~~nhancelllent Division. Washington Departmentof Fisheries. 115 General Admlllistration Building. Olympia. WA <)1;504. Views or opinionsexpressed or implied are those of the author anddo not ncccssarily retlecr the position of theNatiunal Macine Fisheries Service. NOAA.
indexes o/the macrobiota assemblages onrocky reel control areas in the same regionand on consideration a/potential impacts onlisheries and commerce. Experimental designstlIltegies/or hoth the entire hahitat enhancement area and the individual enhancementstructures were used to determine the nptimum balance hetween aggregation and prodUClion u/ target species and management/01' sustained. quality Ii.\heries. Maiorstructured design elemcnts ""ere/ound to be horicOl1/al and vertical relie( and numbers and
local government agencies and serviceorganizations. This provided the broadbase of public awareness and supportwhich resulted in rapid funding of theinitial projects.
During the first 7 years, the conceptsof the marine fish enhancement programhave been well received by the fisheryclientele and have proven relevant tofJshery management in Washington. Biologically. habitat enhancement structuresplaced in open. relatively unproductivemarine locations successfully increasethe areas' density and biomass of biotacommon to productive natural rockyreefs. Sociologically. public fishing piershave become extremely popular accesslocations for shore anglers previouslydenied use of the marine resources. andoffshore "fishing reefs" near metropolitanareas have created valuable recreationalbenefits which are easily accessible toall boat anglers. Economically, habitatenhancement projects and public fishingpiers compete very favorably with otherforms of outdoor recreation for the public funds dedicated to recreational use.
sizes or interstitial spaces. Abundant anddiverse algal growth on the enhancementstructures increases habitat complexity andheterogeneity. and may well be the mostimportant clement in the transition fromintroduced materials tn rqllicates o/productive natural ree/s. Successional developmentollish communities appears to proceed/roma principal(v aggregated species base duringinitia( colonization to a )orager-aggregater"communitv stnlcture as food items developon the enhancement structures.
Marine Fisheries Review
Figure J. - Locations of habitat enhancement areas in Puget Sound, Wash.
@ Public fishing pier
o Fishing reef
facets of the recreational fishery providedthe greatest benefits to the public.
The objective of habitat enhancement,used either in conjunction with fishing
Program Design and Methodology
piers or to create "fishing reefs" for boatanglers, was to establish enhanced areasthat developed biologically into replicates of productive, natural rocky reefcommunities. with resilient populationsof target species of fish which couldwithstand frequent fishing. The biological investigations related to habitatenhancement have been designed tounderstand and utilize the artificial reefsfrom the perspective that the only "artificial factor" in the reef is the originalplacement of the inert base materialaround and upon which the living, natural reef community evolves. An understanding of the factors influencing thisdevelopment enables construction ofhabitat enhancement complexes compatible with environmental and biological constraints.
The increasing demands for improvements in urban recreational fishing opportunities that were being recognizedon a national level in the mid-1970'swere also developing in the metropolitanareas of Puget Sound (pNRBC, 1970;BOR, 1977; Stroud. 1977l. This emphasison urban recreation offered the mostpotentially productive situations whereapplications of marine habitat enhancement would demonstrate the value ofthis technology in modern fishery management.
Many target fishing locations for rockyreef-oriented fishes adjacent to the metropolitan centers of Puget Sound beganreceiving more frequent use in the middleto late 1970's. This resulted from increasing interest in these previously lesspopular fishes. caused, in part, by curtailments in the fisheries for Pacific salmon dictated by the 1974 Boldt Decision(Williams and Neubrech, 1977) on treatyIndian fishing rights and, in part, bydramatic increases in energy (fuel) coststo reach more distant fishing grounds.
Many of these rocky reef sites werelimited in area and habitat diversity and,therefore, supported vulnerable populations of the resident demersal fishesneeded for a continuous fishery. Catchesbegan decreasing in many of the morepopular and accessible locations, andanglers either invested the additional
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i20
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This progress justifies application ofenhancement technology to "real"' fishery management problems, in whichsolutions maximizing accessibility to all
June-July 1982. 44(6-7) 29
Figure 2. - The Edmonds Public Fishing Pier.
costs to travel to more productive locations, modified their criteria for productive catches. or withdrew from thefishery. Strong public sentiments developed for more productive urban fishinglocations accessible (economically) to abroad spectrum of recreational anglers.The use of marine habitat enhancementto create productive nearshore fishingsites was an obvious and timely solutionto this problem.
The introduction in 1975 of largepublic fishing piers (Fig. 2) to the urbanrecreational fishery scene in Washingtonpresented an excellent "vehicle to gainvisibility" for marine habitat enhancement in an essentially risk-free manner.Metropolitan areas in Puget Sound hadthe potential for developing a large pierfishing clientele, but there were no available facilities designed and sited specifically for recreational f]shing. Most ofthe metropolitan centers bordered marine waters with good biological production potential and excellent fishingdepths (from -27 to -55 m MLLWImean lower low water j). This new urbanfishery was virtually guaranteed to pro-
30
vide popular. accessible. and affordableparticipation in marine recreationalfishing for all anglers. regardless of ageor physical ability (Buckley and Walton.1981 ).
The public fishing piers in PugetSound created intense. concentratedfisheries that could not enjoy sustainedcatches without dramatically increasedaggregation and production of importantspecies of fish in the pier areas. Theconstruction of large habitat enhancement complexes around the piers increased the areas' prnJuction of residentand semiresident species, and providedfeeding and orientation sites for aggregation of transient species- both important in sustaining quality catches in acontinuous fishery situation. This combination of fishing piers and habitatenhancement brought the concepts andbenefits of habitat enhancement intocontact with the maximum number ofanglers in a "high profile" fishery at thestart of the marine fish enhancementprogram.
Later use of habitat enhancement tocreate "fishing reefs" for the boat fishing
clientele was the first application of thistechnology to benefit an establishedrecreational fishery in Washington.These "boat angler reefs" were sitedevery 18- 28 km along the 185 km cruising route from southern Puget Soundnorth to the San Juan Islands. and werealso accessible from major recreationalfishing boat launch facilities. This provided the opportunity both to occasional"yachting anglers" and avid small- boatanglers, representing the bulk of therecreational fishing effort on PugetSound, to utilize habitat-enhanced fishing locations.
The base of interest and support forthe marine fish enhancement programthat developed in the public sector wascomplemented by the very importantacceptance of the same concepts withinthe relevant scientific community. Thisresulted primarily from the promotionand use of marine habitat enhancementas a fishery management tool whichsecondarily had the capacity to recyclespecific types of solid wastes under ecologically acceptable conditions. Thereis some evidence that earlier local (and
Marine Fisheries Review
national) emphasis on relating artiucialreef construction to deposition of a variety of solid waste materials in the marineenvironment resulted in waste disposaloften being perceived and promoted asthe primary justincation for reef construction. A further consequence of thismisconception was the trend that artificial reef projects had to be minimalbudget operations supported by donations of materials and volunteer labor.which led to the traditional corollarythat artificial reef projects did not requirepublic funds and. therefore, had littleintrinsic value. In contrast, the representation of marine habitat enhancementas a valid fishery management techniqueworthy of investment, the same as freshwater fish-producing facilities (and lacking anything synonymous with the term"artificial"), utilized this traditional viewin a positive manner and supported theinvestment of public funds through theuse of donated materials. when appropriate.
The Washington Department of Fisheries receives construction funds formarine fish enhancement projects as partof the State legislative biennial appropriations for the agency's Capital Outdoor Recreation Budget. The source ofthese appropriations is a 50 percent StateGovernment/50 percent Federal Government matching fund administeredthrough the State's Interagency Committee for Outdoor Recreation. TheState's share of the fund is obtained fromvoter-approved Referendum Bonds forrecreation. The Land and Water Conservation Fund. administered by theHeritage. Conservation. and RecreationService (absorbed by the National ParkService in June 1981) of the Departmentof Interior. supplies the Federal matchingfunds. The implementation of thesecapital appropriations, and the researchsupporting the marine ush enhancementprogram, are funded by the biennialOperational Budget of the Marine FishProgram.
Since the inception of the marine ushenhancement program in 1974, $3.2million in capital funds have been appropriated for marine habitat enhancement and public fishing pier projects.The 1981-83 Capital Budget included$2.5 million for 14 habitat enhancement
June-July 1982. 44(6-7)
projects, three associated with publicfishing piers. An additional $1.2 millionis scheduled for appropriation for another fishing pier project in 1983. Thisfunding base. which has established twopublic fishing piers and two "boat anglernshing reefs" and has one fishing pierand eight fishing reefs under construction. is only as stable as its two fundingsources. Anticipated Federal reductionsand delays in the Land and Water Conservation Fund appropriations to thestates in 1982 will cause severely curtailed construction schedules. and havecreated interest in establishing a 50 percent Federal Government/50 percentlocal government matching fund approach for some projects. This releaseof State Government funds would enable100 percent State funding of some projects. if current economic inflation factorsdo not prohibit continued sale of recreation bonds.
Site Selection, FacilityDesign, and Fishery Management
Successful biological development ofhabitat enhancement projects in marinewaters is a key prerequisite to productivefisheries on the enhancement structures.To maximize the potential for biologicaldevelopment, a site-selection processwas used which relied heavily on a biotaindexing comparison system developed
Figure 3. - Auto- tire artifact on sand substrate.
for the Puget Sound region (Hueckeland Buckley'). This system was basedon indexes of the macrobiota assemblages on three natural rocky reef controlareas which had stable. diverse communities of algae. invertebrates. and fishes,and were productive recreational fisherysites. Biota common to all three areaswere assumed to typify those that wouldoccur on habitat enhancement structuresplaced in areas with the environmentalparameters conducive to productivebiological development.
Transects conducted on potentialhabitat enhancement sites qualitativelyassessed the biota in relation to prevailingsubstrate characteristics. Artifacts andsubstrate anomalies on the site (such asatypically large rocks. logs, and manmade debris, Fig. 3) were examinedcarefully. Their attached and relatedbiota were representative of the biotathat would develop on the site with theaddition of stable material to increasethe diversity and relief of the substrate.A high percent overlap between thecontrol site and enhancement site biotawas indicative of a good habitat enhancement site. although the opposite relationship was not necessarily true. espe-
'Hueckel. G. J.. and R. M. Buckley. Site selection procedures for marine habitat enhancement in Puget Sound. Washington. In prep.
Figure 4.-Scrap concrete used for habitat enhancement construction.
cially if rocky reef simulating substrateswere not available.
The site-selection process also considered several other factors relevant toensuring that the habitat enhancementstructures attracted desirable biota andfishery utilization, and not unwantedsediments or commercial fishery nets.Conflicts with existing and future fisheries were analyzed to avoid overlappingutilization of the area, if possible, or todetermine the most beneficial use of thesite. Conflicts with commercial vesseltraffic were avoided, both in relation tovessel draft restrictions caused by theenhancement structures and to surfacecongestion caused by fishing boats. Theproximity of the enhanced site to recreational access locations was also important to facilitate utilization and. therefore. maximum public benefits.
Various design strategies for both theentire habitat enhancement areas andthe individual enhancement structureswere used to determine the optimumbalance between aggregation and production of target species and management for sustained, quality fisheries.These experimental design considerations required habitat enhancementconstruction techniques that went farbeyond the "random dump and hope"methods used in earlier artificial reefprojects, occasionally involving underwater construction and placement ofenhancement structures by scuba divers.
The habitat enhancement complexessurrounding public fishing piers coverfrom 1.5 to 2.0 hectares, which are farlarger areas than can be fished from the
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piers. This design strategy makes 20-30percent of each pier's enhanced areaaccessible to pier angler's gear. andallows the bulk of the enhancementstructures to build reserve populationsof resident and semiresident fishes toreplenish removals by the pier fishery. Acompanion management strategy reserves these populations for pier anglersby closing the enhancement areas to allother fisheries. The "extra large" enhanced areas and the associated biotaalso serve as attractive target feedinglocations for transient (often pelagic)species of fish. holding them within reachof the pier fisheries for ex tended periods.
Individual habitat enhancement structures are located either under the pier oroutside of a 2:\- 30 m perimeter surrounding the pier. This creates an "open zone"around the pier to minimize gear foulingon the enhancement structures andmakes both open sand- bottom and rockyreef fish species available to the pierfishery harvest. Conservative harvestmanagement regulations are being testedto provide recreational enjoyment atreduced levels of impact on these, usuallyresident. target species.
The habitat enhancement complexescreating fishing reefs [or boat anglersutilize up to 10 hectares of the bottombetween the -1:\ to - 27 m MLLWdepths. These rather extensive areasallow a design strategy that distributesand spaces both the enhancement material and the ensuing fishing effort.Research has shown that large peripheralopen feeding areas are important to somerocky reef [lshes during specific life
history stages (Hueckel and Stayton.19R2) and that aesthetic enjoyment in arecreational fishery can be increased byreducing crowding in the fishing area.An extensive enhanced area also enablesmanagement strategies that disperse orrelocate fishing effort to reduce the impacts on fish populations inhabitingspecific enhancement structures, suchas spawning aggregations, juvenile recruitment areas, or overfished targetlocations. This can often be accomplished by utilizing the "magnetic buoyfactor" which results in recreational anglers fishing only around the buoy thatmarks the fishing reef. Fishing effort canbe evenly distributed by periodicallymoving the buoy to different locationsthroughout the enhanced area.
Theoretically. a fishing reef for boatanglers is totally accessible (if totallylocatable), and it is not practical to offsetfishery removals through building reservepopulations of fish by closing a portiono[ the reef to fishing. The potential foroverfishing is, therefore, much greateron a boat angler's fishing reef than in anenhanced area associated with a fishingpier, and this factor must be consideredin the fishery management strategy. Conservative harvest management regulations are usually inappropriate in thesesituations. as they would have to applyto large geographic areas surroundingthe fishing reef to be enforceable andwould unnecessarily restrict otherfisheries.
Experimentation with the design ofthe individual habitat structures is beingexamined as a method to control therate of fishery removals over a longperiod of time, especially for the residentand semiresident species which utilizethe structures for productive habitat.Enhancement structures constructedfrom large, angular material (such aslong, flat concrete planks, Fig. 4) createlarge cave-like habitats which have ahigh refuge potential from anglers' gear.This reduces (or controls) the fishabilityof the enhancement complex throughphysically preventing frequent contactbetween fish and fishing gear, but stillallows harvest of those fish on the periphery of the structures. This construction technique also appears to minimizegear fouling on the structures.
Marine Fisheries Review
Figure 5. - Rockfish (Sebastes sp.) utilizing small habitats on an auto- tire module.
Habitat Design, Colonization,and Ecosystem Development
The design of the marine habitat enhancement program in Puget Sound isbased on directing the biota developmenton. and in close association with. thehabitat structures toward a multispeciesand multilife- history stage community.This follows the premise that biota diversity will lead to productive, relativelystable communities of organisms whichhave the resiliency to respond to fisheryremovals throughout development. However. it is apparent from other researchthat this premise may be flawed. Indiscussing a general hypothesis of speciesdiversity, Huston (1979) pointed out thatdiversity has been both positively andnegatively correlated with productivityby many authors. Sale and Dybdahl(1975) found that communities of coralreef fishes are likely to demonstrate onlyweak stability and that the equation"diversity = stability" has questionablevalidity. A saving (or modifying) factormay be that most of this work relates totropical patch- reef situations and maynot be totally applicable to temperaterocky reefs. Sale and Dybdahl (1975)also pointed out that a fuller understanding of community structure (andresponses?) will urgently require fargreater information on the biology ofthe species involved.
The work carried out to date in Washington's marine habitat enhancementprogram has shown that the design andrelative spacing of enhancement structures influence ecosystem developmentin the enhanced area, from initial placement of the structures throughout theirlong- term development. Major structuraldesign elements are 1) horizontal andvertical relief and 2) numbers and sizesof interstitial spaces. The latter elementdirectly affects the sizes of the morecryptic fishes that colonize the structuresand may also influence the species offish and the sizes of some invertebrates.The spacing and sizes of the habitatstructures affect the amount of interfacewith the surrounding pelagic and benthicenvironments, which has, as yet, an incompletely understood effect on interstructure relationships. It has beendemonstrated that maintaining open
June-July /982, 44(6-7)
zones within the enhancement areas isbeneficial to both reef species (Hueckeland Stayton, 1982) and nonreef species(Walton, 1979).
Current literature on reef colonizationsupports the view that determination ofthe actual factors controlling this processis a continuing question. especially intemperate regions (Fager. 1972; Talbotet al.. 1979; Stephens and Zerba. 1981;and others). Brock et al. (1979) examinedrecolonization in coral reef communitiesand found that "the structure of reef fJshcommunities may be the result of amosaic of deterministic patterns andstochastic processes that occur duringinitial colonization and continue throughtime." This fInding supports the generalconsensus in the literature that the various resource-partitioning, spacelimited. predator-limited, lotteryhypothesis. resource-sharing viewpointsall have their own areas of credibility asmechanisms which influence colonization, diversity, and stability in reef fishcommunities. For example, Russell etal. (1974, in Brock et aI., 1979) workingon the Great Barrier Reef, noted thatthe physical structure of artifIcial reefhabitats was relatively unimportant indetermining early colonization community structure, and Nolan (1975, inBrock et aI., 1979), working in the Mar-
shall Islands. could not find any obviouscorrelation between artificial reef substrate complexity and fish species diversity. However, Walton (1979), workingin the Pacific orthwest, found that thestructural design and physicaJ placementof artifIcial reef modules affected thedensity and biomass of associated fIshpopulations.
The structure of temperate reef fIshcommunities in Puget Sound may beheavily influenced by chance factors onthe species level, as long as suitably sizedhabitats are available to meet the needsof the life history stages (sizes) of thespecies recruiting to the reef (somewhatdeterministic biological patterns'!).RockfIsh (Sebasles sp.) colonization ofthe auto-tire module and rubble rockenhancement structures associated withthe Edmonds Public Fishing Pier followed a defInite pattern of associationbetween fIsh size and habitat selection.Small interstitial spaces formed by rubblerock were utilized by small rockfIsh upto 15 cm in length, and tire modules(triads) with large cave-like openings andsmall crevices showed rockfIsh distributions based directly on habitat size (Fig.5.6). This same pattern was observed inthe initial colonization of scrap concreteenhancement structures at Gedney Island by hoth juvenile and adult rockfJsh,
]3
Figure 6.-Rockfish ISebasles sp.1 utilizing a large habitat on an aUla-tire module. Figure 7.-Juvenile rockfish (Sebasles sp.) utilizing a narrow protective habitat.
where (protective?) habitat selection wasstrongly size- related and the area appeared to be habitat-limited for juveniles(Fig. 7).
The suitability of the habitats formedby enhancement structures has also beenobserved to affect initial colonization bysuch diverse biota as 8 cm shrimp and100 em predatory fish. Protective habitatfor the coon-striped shrimp, Pandalusdanae. a major food item for many fishes,consisted of the smaller interstitial spacesand often included the same crevicesused by juvenile rockfish which wouldlater become shrimp predators. Spawning territories for lingcod, Ophiodol1elongatus, were established at sites withthe appropriate semiexposed crevicehabitats suitable for retaining large eggmasses (up to 0.5 m diameter). whichsolidify to the shape of the crevice to
34
prevent dislodging when washed by tidalcurrents (Fig. 8).
Selection of construction materialsand techniques which allow optimumvertical and horizontal distribution of avariety of interstitial spaces provides thebest potential base for successful habitatenhancement in local marine waters.Equally important. however, are thelong- term physical and chemical stabilityof the construction materials and theamount of photic-zone exposure of theenhancement structures, hath of whichinfluence algal community development.Scrap concrete. auto tires. and quarryrock are all acceptable substrate materials. offering firm. textured surfaces,although concrete is currently the mostcost-effective, durable. and structurallydesirable for local marine habitat enhancement.
Abundant and diverse algal growthon the enhancement structures significantly adds to habitat complexity andheterogeneity. allowing more species andmore organisms to coexist in the enhanced areas. This may well be the mostimportant element in the transitionfrom introduced materials to productivenatural reef replicates with stable communities. Sessile algae are major contributors to the physical structure of communities in the marine environment(Fager. 1972). and the microhabitatscreated by their holdfasts and upperstructures are used extensively by avariety of invertebrates that are potentialfood organisms (Hueckel. 1980). Theincreased predator- prey interactionsavailed by the increased production offood items provide greater choices forenergy transfer through the food web in
Marine Fisheries Review
Figure 8. - Male lingcod. 0. elongGtu5. guarding an egg mass.
the community, and the number of linksin the food web is a measure of thestability of the community (Odum, J953in MacArthur. J955).
The successional development ofalgae and invertebrates on substratesintroduced into the marine environmenthas been well documented for manyregions (Coe and Allen, 1937; Tsudaand Kami, 1973; Saito et aI., 1976).Hueckel (1980) studied colonization ofauto tire habitat enhancement structuresat the Edmonds Public Fishing Pier for24 months (1977-79) and found that algaldevelopment was very important to subsequent invertebrate colonization: "Priorto algal colonization, only Ithe crevicerelated I coon-striped shrimp (Pandalusdanae), two species of starfIsh (Pycnipodia helianthoides and Evasteriastroscheli), acorn barnacles (Balanus
June-July /982, 44(6-7)
glandula), and a sea anemone (Metridiurn senile) had been observed on thetires. After the development of algae onthe tires, large numbers of gammaridamphipods, caprellid amphipods, harpacticoid copepods and hippolytidshrimp were observed associating withthe algae .... Platytharnnion pectinaturnwas the dominant red algae IRhodophyceae I species on the artifIcial reefthroughout the study. The fIlamentousstructure and profuse branching of thisspecies provided refuge for most of themicroinvertebrates on the artifIcial reeL"Walton (1979), studying the same enhancement structures, found that thespecies and numbers of fish increasedwith the age (increased development) ofthe habitats, the same pattern of development noted on nearshore artificialreefs in California and related to increas-
ingly available food and shelter (Turneret aI., 1969).
Acorn barnacles colonized the Edmonds enhancement structures in highnumbers during the first spring, followedby rapid mortalities over a 4-month period, and never regained the initial highconcentrations (Fig. 9). There is goodevidence that this decrease was directlyrelated to grazing by starfish (F. helianthoides and E. troschelt) and surfperch(Embiotoca lateralis and Rhacochilusvacca). Subsequent algal colonizationoccurred on the basal plates left aftergrazing and may have inhibited barnaclerepopulation by preventing the larvae(cypris) from setting on the solid substrate. Red algae dominated the enhancement structures (approximately 95percent coverage by F. pectinatum, and5 percent by Callophyllus spp. and Poly-
]5
Figure 10. - Percent coverage of algae on habitat enhancement structures at theEdmonds Public Fishing Pier (from Hueckel, 1980).
Jan1979
Jan1979
Oct
Oct
Sampling deplhs
0--0 = 10 m•..... = 12 mrr---A = 15 m
Jan1978
S8JT'4*lg deplhs
<>--<> = 10 m..... =12 m6----6 = 15 m
.'.
Jan1978
-.
•., l..•..,? \, .•
. . ."Lf,'
0--0-""" ..
Oct
Oct
·, .· .· ,... \
"\....•----~,. \,
.. ~. '-
.All
"T.~·\. . .
100
Figure 9.- Percent coverage of the acorn barnacle. Balanus glandula, on habitatenhancement structures at the Edmonds Public Fishing Pier (from Hueckel. 1980).
80 .' .•<»Cl.. 60Q;>00
C<»~ 40<»"- .
""·.· ,· .20 · ,
. · \,.' \ "
:
0
Apr ~I
1977
lOll
80
&e 80<»>00
i0 40~"-
20
neura latissima) and commenced to showthe expected seasonal abundance cycle(Fig. 10).
This enriched habitat on the enhancement structures supplied microinvertebrate prey organisms «2.5 cm in length)in concentrations up to 400/m2
, andmacroinvertebrate prey organisms (including coon-striped shrimp) in concentrations up to 371m2 (Hueckel, 19S0).Combined with additonal prey organismsoccurring naturally in the surroundingsand substrate (Table 1), the entire enhanced area adjacent to the EdmondsPublic Fishing Pier provided a productivefeeding location for many species of fish(Hueckel and Stayton, 1982).
It is interesting to speculate (and possibly worth future consideration) whetherecosystem development on habitat enhancement structures could be controlled, or periodically altered. to increase the abundance and types of preyorganisms. For example, would the introduction of large numbers of herbivores on some of the enhancementstructures at Edmonds graze down thealgae and allow recolonization by acornbarnacles? Could this be carried outimmediately adjacent to the fishing pierto pr.ovide a prime feeding site for surfperch, which would be removed by thepier ushery before they could heavilyimpact the barnacle population. leavingan abundant food source to attract moresurfperch (baited-trap equilibrium?)?Sale (1977) expressed the view that thediversity of coral reef fish communitieswas directly correlated with the rate ofsmall-scale, unpredictable disturbancesto the supply of living space, and thatthis could be tested experimentally bymanipulating the rate of disturbancethrough increased predation (spear ushing). It seems equally plausible to experimentally control sessile and motile
Table 1.-Prey organisms identified in benthic cores,benthic plankton-net tows, and successional development studies in the habitat enhanced area at the Ed·monds Public Fishing Pier, August 1977-December1978.
Percent
Habitat enhancement SandPrey organisms structures substrate
Microinvertebrates' 80 46Caridean shrimp 20Polychaete annelids 33Bivalve mollusks 15Nematodes 6
'Less than 2.5 em in length.
invertebrate populations on island-likeenhancement structures.
Long.Term Fish Community Structure
The successional development of fishcommunities on habitat enhancementareas in Puget Sound appears to proceedfrom a principally aggregated speciesbase during initial colonization to a"forager-aggregater" community struc-
ture as food items develop on the enhancement structures. A composite ofresearch information from several enhancement areas shows that the earlycolonizing ushes represent 1) uve speciesof aggregaters, averaging 43 g each.which utilize the habitat structures fororientation and protection while feedingprimarily on organisms from the surrounding benthic and pelagic environ-
36 Marine Fisheries Review
Table 2.- Harvests at residenl (R), semi resident (S-R), and transienl-feeding (T-F) fishes fromthe Edmonds Public Fishing Pier.
Fishery year First qtr 1 Second qtr. Third qtr Fourth qtr Total
March 1979- R ' S-R 922 813 68 38.4 32.6March 1980 T-F 7.8 18.7 932 61.6 67.4
May 1980- R , S-R 83.5 22.5 496 65.8 401May 1981 T-F 16.5 77.5 50.4 342 59.9
'Quarters overlap only 1.5 months between fishery years.
ments, and 2) two species of (predatory)foragers, averaging 1.553 g each, whichutilize the habitat structures as a placeto feed on structure- related organisms(principally aggregated (lshes), Afterseveral years of biological development,the fish community structures change torepresent five species of aggregaters,averaging 545 g each, and eight speciesof foragers, averaging 364 g each, withat least 60 percent species overlap ineach group. These disparities in averagesizes of early colonizing fishes demonstrate that the aggregaters were primarilyjuveniles (seeking unoccupied habitat?)and the foragers were (wandering?) adultpredators, In comparison, the averagesizes in the developed fish communitiesdemonstrate a more balanced distribution of all aggregater and forager lifehistory stages, This pattern of early colonization of reef structures by mainlyjuveniles, with some (itinerant) adultfishes, has been reported by many researchers (Talbot et aI., 1979; Brock etaI., 1979; and Stone et aI., 1979),
Persistent aggregation of fishes byhabitat enhancement structures is veryimportant to continued fishery utilizationof the sites, Foragers represent many ofthe resident and semiresident species thatare limited in abundance by the amountof food and habitat (area) provided bythe enhancement structures. The aggregaters include the transient species thatutilize the enhanced areas as "patchy"feeding locations in rather broad geographic regions. These large populationsoccur intermittently in the target fishinglocations, providing excellent catchesand reducing pressure on resident andsemi resident stocks, but are less vulnerable to overharvest. The first two fisheryyears on the Edmonds Public FishingPier produced harvests dominated bythe transient-feeding fishes (67.4 and59.9, respectively), but quarterly catchestimates demonstrated the equally im-
June-July 1982, 44(6-7;
Percent of harvest
portant role of the resident and semiresident fishes in carrying the fisherythrough less productive periods (Table2).
Stone et al. (1979) are the most recentresearchers to show that marine habitatenhancement (an artificial reef) will increase carrying capacity and reef fishbiomass in the immediate vicinity of anatural coral reef, without diminishingthe resident population of the naturalreef through attraction to the new habitat. Similar results have been found tooccur in local temperate waters betweennew and old habitat enhancement structures which simulate rocky reef-likehabitats. A quarry rock breakwaterrubble rock- covered pipeline habitatestablished in 1968-71, had fish densitiesaveraging 0,27 fish/m1 (quarterly, July1975 to June 1976) just prior to construction of an adjacent tire- moduleartificial reef (Walton, 1979). Five yearslater, fish densities on this habitat hadincreased to 0.44 fish/m 2 while the tiremodules had developed fish populationsof 1,77 fish/m1 (Washington Departmentof Fisheries survey data),
These examples of an absence of longterm detrimental effects between thenew and old habitats, and the apparentrelatively independent development ofassociated fish populations, support theidea that increasing the amount of reefsimulating habitat in the nearshore marine environment increases fish production. Local marine waters do not (currently) represent a nutrient-limited system that can be adversely affected by anexpanding habitat enhancement program;in fact, there is a closer representationof a habitat-limited system that respondsto increased habitat diversity with increased production of desirable biota.
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