NEW DEVELOPMENTS IN THE ZOO WORLD I l l

Inl. Zoo Yb. (1992) 31: Ill-I15 The Zoological Society of London

Captive care of and research on Arctic fish and invertebrates MARK GRAHAM' & KEN WONG2 ' Curator of Fishes and 2Aquarist, Vancouver Public Aquarium, In Stanley Park, PO Box 3232, Vancouver, British Columbia, Canada V6B 3x8

There are few unexplored and unre- searched environments within reach of our terrestrial domain. The last strong- holds of the wild, the most difficult areas in which to work, are currently stimu- lating the interest of the general public and scientists alike. Space, the deep ocean and the polar oceans are areas of explora- tion that require enormous amounts of technology to discover, commensurate with enormous cost. This report deals with recent advances in Arctic marine biology and outlines the importance of research and interpretation of this region.

Marine science in polar regions is a relatively new area of discovery. Owing to the severity of the climate, these areas have defied exploration by scientists for centuries. Now there are several research facilities at both poles and information about polar biology is being gathered. However, our understanding of the biology of the marine fauna and flora is still far from complete.

The scientist's fascination with the Arctic has attracted the attention of the general public. This attention has been accommodated by making the polar reaches accessible to tourists and adven- turers. Exhibits of Arctic marine animals have been initiated at lower latitudes, providing a less expensive Arctic experi- ence. In May 1990 the Vancouver Public Aquarium opened Arctic Canada, a multimillion-dollar complex depicting different ecological facets of the Lancaster Sound area. The Arctic Canada complex includes a display facility for five Beluga whales Delphinapterus leucas and a display of Arctic fish and invertebrates. A

holding facility for Arctic fish and inverte- brates has been operational since the summer of 1989.

Although exhibits of terrestrial Arctic vertebrates have been in existence for decades, these carnivores represent the upper strata of the food web and are minor players energetically speaking. What visitors to the Arctic do not see readily are organisms that live below the surface of the ocean: kelp, phytoplankton, fish and invertebrates. There are local names for most of the zooplankton, bottom fauna and fish, because they have become familiar through being taken ashore by storms and ice or found on the end of a hook, in the stomach of large game or in a gill net. Nevertheless they are small, rare samples of animals about which even the native peoples know little. In terms of the marine ecosystem, however, these organisms are most impor- tant. Sampling by otter trawl, plankton tow or with scuba allows a more thorough appreciation of the members of this cold ecosystem.

Public displays of Arctic marine fish and invertebrates have only recently been introduced. The exhibits and holding faci- lities have also opened up avenues never before possible in Arctic marine research. Scientists have maintained collections in holding tanks during the course of observations and experiments but long- standing exhibits and holding facilities have not been apparent. There are several reasons for this omission. The early Arctic exhibits reflected the most prominent and easiest fauna to access, that is, the animals that live on and around the ice and land.

112 NEW DEVELOPMENTS IN THE ZOO WORLD

Working with boats in the Arctic is dangerous at the best of times and exploration below the sea surface was restricted to trawling from large ships for taxonomic studies and life-history strategies of the plankton. With the recent development of permanent camps for year-round work, divers and trap nets have been used to capture live specimens in ideal condition for long-term study and exhibit. Furthermore, the logistics of travelling to capture sites, capturing, transporting and keeping animals at 0°C are not easy. Closed-system aquaria at 0" are expensive to establish. Because they are uncommon it is not surprising that there is no literature on the function of such facilities and some cautious experi- mentation was required.

The advanced facilities at Vancouver Public Aquarium made use of three types of aquaria suitable for Arctic marine aquaria, two types of closed-filter systems and an open-aquarium system. The work- ings of these are outlined below.

CLOSED-FILTER SYSTEMS Two separate facilities were established each using a different type of filtration system: the first a submerged filter medium of compact plastic brushes and the second a traditional trickle filter using trays of plastic rings as the filter medium. From our observations it was apparent that both filters could support an equiva- lent bio-load per equivalent amount of filter medium. One significant difference of the trickle-filter system was the extra refrigeration required to hold the water temperature at 0°C because of the addi- tional exposure to air at 20°C. A further complication with this filter was the increased amount of water loss through evaporation compared with that of the submerged filter. The data below are for the submerged filter.

Initially the submerged filter bed was established by seeding the system with raw sea-water and filter medium from an established system, and providing a

nitrogen source through the addition of fish to the tank. This was done at 1 I-13°C for seven days (Fig. le). Water tempera- ture was lowered to 2 4 ° C by day 10 and held there for a four-week period before being lowered to its permanent tempera- ture range of 0-2°C. During this period of establishing a nitrogen cycling there were features typical of those seen for closed- systems at higher temperatures: ammonia peaks, followed by nitrite build-up and a later accumulation of nitrate (Fig. la, b, c).

A significant departure from warm- water systems was the length of time taken for nitrates to accumulate (Fig. Ic). Typically, as nitrite concentration falls off in a new system, there is corresponding accumulation of nitrates (Bower, 1983). The latency of this event in the Arctic aquarium system may have been due to a significant temperature effect upon nitri- fying bacteria, such as Nitrobacter, Nitro- spira, Nitroc-vctis and Nitrococcus. The regular water changes of 10% total volume per week may also have had an effect. This water change with ambient sea-water allowed dilution of nitrogenous wastes, while not warming the water significantly. [f temperature did affect this group of bacteria, it did not have the same effect on the organisms that convert ammonia to nitrite, such as Nitrosomonas. The ammonia peaks that occurred until day 17 (Fig. la) coincided with bio- loading with north Pacific fishes.

The filter consisted of 50 brushes of 60mm diameter and 470mm length. The bristle density was 83/1 mm brush length, providing a surface area of 166 067 mm2/ brush or 8 . 3 ~ 106mm2 per filter (or 8.3 m2). This configuration has supported up to 5 kg (wet mass) of fish and inverte- brates. Each of the holding facilities contained 1000 litres of sea-water (800 litres in the specimen tank and 200 litres in the filter box). A foam fractionator operated directly off the filter box. A 0-5 hp compressor was able to hold water temperature at 1-2°C (a 20" differential between water and air temperature), while

NEW DEVELOPMENTS IN THE ZOO WORLD 113

B

NO3

*OT

C t

51

O C

0 5 15 ' 25 35 4'5

l 5 I u 11

E

L, 5 15 25 35 45

days

1 I 20 40 50 80 100 120

days

Fig. 1. Sea-water chemistry (A-D) and temperature (E) for a submerged filter system: A. total ammonia concentrations in mg/Mtre; B. total nitrite concentrations in mgptre; C. total nitrate concentrations in mg/litre; D. oxygen concentration in mg/litre (top line) and pH (bottom line); E. water temperature. The time wale for nitrate values (C) is different from that for the other data. Chemistry values were determined with the DreU 5 system (Hach, Colorado) (Anon., 1985). The use of these methods allowed a detection of ammonia concentration only to a maximum of 0.8 mgmtre.

a 0.75 hp compressor could maintain water temperature at 0-1 "C.

ANIMALS HOUSED On day 20 of the filter operation the local fish were replaced by a large number of Arctic fish and invertebrates (Table 1); reflected in the ammonia peak on day22 (Fig. la). The animals were all collected by hand nets and trap nets from Resolute Passage and Resolute Bay, in the area of Cornwallis Island (75"N, 95"W). After holding for one week to allow for near total gut evacuation (Arctic cod Boreo- gudus saidu fed to satiation require a full two weeks for total evacuation of the gut (H. Hop, pers. comm.)), the fish were contained in plastic bags inside thermally

protected boxes with copious amounts of ice for the 20-hour trip to Vancouver.

OPEN-AQUARIUM SYSTEM In August 1990 the world's most north- erly situated public aquarium was opened in Resolute, Northwest Territories. Reso- lute is a crossroad to many locations in the Arctic, has a native settlement and is the site of a permanent marine research centre, financed by the Department of Fisheries and Oceans, making it an ideal site for a public aquarium. Together these factors ensure that each year hundreds of visitors see the three large displays and receive interpretation on the marine environment.

The Resolute Bay Aquarium is also the

114 NEW DEVELOPMENTS IN THE ZOO WORLD

FAMILY SPECIES HOUSED

FISH Gadidae (codfish) Zoarcidae (eelpouts)

Cottidae (sculpins)

Cyclopteridae (lumpfish and snailfish)

INVERTEBRATES Seastars

Sea urchins

Soft coral Anemones

Bivalve molluscs

Large isopods

Boreogadus s a i h Gymnelis viridis Lycodes polaris L. reticulatus Icelus sp Myoxocephalus

quadricornis M. scorpioides Cot tunculus microps

Eumicrotremus derjugini Liparis sp

Crossaster papposus Leptasterias sp Strongylocentrotus

droebachiensis Gersemia rub iformis Urticina sp' Hormathia sp' Hiatella arctica Mya truncata Serripes groenlandicus Arcturus baffini

'Identification uncertain.

Table 1. Arctic fish and invertebrates housed in the closed-filter system tank at the Vancouver Public Aquarium.

ideal aquarium in its mode of operation. It is in use only during June to September, the period of highest visitor traffic, both of tourists and researchers. After that period the animals are returned to the Bay to be replaced the following season. Sea- water can be pumped direct into the tanks without filtration giving the best water conditions for the many species of filter- feeding invertebrates. As in the display tank in the Vancouver Public Aquarium thick acrylic glazing, a more effective insu- lator than glass, is necessary for the viewing windows of the tanks. Even with the use of 2-5 cm thick acrylic, condensa- tion will form if a strong current of air is not directed across it.

The Resolute Bay Aquarium has inter- pretative graphics that explain the biology of pelagic, mud bottom and rocky habi- tats, as well as identification labels for the

more common species. All the text is in English and Inuktitut. An automated audiovisual slide presentation gives information on current findings about the Arctic marine ecosystem. As in many other public aquaria, it has proved extremely valuable to have a closely related research interpretation together with the natural history interpretation.

RESEARCH ON CAPTIVE STOCK A functioning biofilter and ample holding space at 0°C has provided a great poten- tial for research. The difficulties of experi- mentation in the Arctic are more forbidding than in an established labora- tory. Investigations into the energetics of Arctic cod have been undertaken in Vancouver. After eight months in the aquarium, healthy growing cod were fed to satiation or fasted until their guts were empty before assessment of their oxygen requirements. The work is facilitated with acclimatized captive stock because the fish are well adapted to taking prepared food, feed well and appear less active in confine- ment than fish newly caught from the wild. The energetic values will provide the most conservative data for routine meta- bolism, thus avoiding artificially elevated metabolic rates related to capture stress (Holeton, 1974).

For the past two years, during the months of February, adult cod (three years of age and older) have spawned in the holding facility. It is possible to ferti- lize eggs in a dish and incubate them (70 days) until hatching (cf. Aronovich et af., 1975). To date we have failed to initiate feeding in our captive-bred stock, although Aronovich et af. (1975) reported success in rearing larvae. Data for com- parison are provided by a number of studies on spawning in the wild (Baranen- kova et al., 1964; Rass, 1968; Altukhov, 1981; Craig et af., 1982; Sameoto, 1984). Because cod spawn under the polar ice (Sameoto, 1984; Bradstreet et al., 1986), it is not easy to observe and quantify repro- ductive processes. Captive adult cod have been reared to reproductive age in

NEW DEVELOPMENTS IN T H E ZOO WORLD I15

Vancouver and have provided data on the morphometrics of this life stage and of the eggs, and the meristics of the larvae. Serum samples from this group have also provided material for reproductive hormone profiles.

Clam populations, which are vital food for large mammals, such as Walrus Odo- benus rosmarus, have been the subject of research by scientists at the Resolute faci- lity for many years. In the last year they have established clams in natural sedi- ments in display tanks and took note of various as yet unquantified processes. For example, the rate of burial, the jet-like expulsion of pseudofaeces, filtration rates and oxygen requirements.

There is an obvious potential for feeding behaviour and predation experi- ments in such facilities. One particular curiosity which we would be interested to investigate are the zoarcids, which seem content to use a combination of crawling and snake-like motion to hunt bottom- living invertebrates or to nip off the feeding tentacles of sea cucumber or the fragile siphons of Mucoma species.

CONCLUSION Much more research is required before we fully understand the closed-system filtra- tion at Arctic water temperatures. For instance, the temperature sensitivity of key bacteria species in processing nitroge- nous compounds needs to be defined. Meanwhile, it has been shown that exten- sive collections can be kept over long periods in good condition (to date, as long as three years) and that the holding systems can be put to good use in research and interpretation of an ecosystem we still know very little about.

ACKNOWLEDGEMENTS

Thanks are due to the numerous aquarists at the Vancouver Public Aquarium who regularly contribute to the care of the Arctic water systems there. Also the Department of Fisheries and Oceans,

Canada, and the scientists at the South Camp at Resolute contributed generously towards establishing the upkeep of the Resolute Bay Aquarium. Dr Harold Welch provided the stimulus for the creation of the Resolute Aquarium and also the logistic support in collecting the fish and invertebrate specimens for the Arctic display in Vancouver. Financial support for this work was provided by the Vancouver Public Aquarium, Department of Fisheries and Oceans, and the Ministry of Economic Development and Tourism. Government of the Northwest Territories.

REFERENCES ALTUKHOV, K. A. (1981): The reproduction and development of the arctic cod, Boreogadus saida, in the White Sea. J . Ichthyol. 19 93-101. ANON. (1985): Hach water analysis handbook 2. Colorado: Hach Co. ARONOVICH, T. M ., DOROSHEV, S. I., SPECTOROVA, L. V. 8r MAKHOTIN, V. M. (1975): Egg incubation and larval rearing of navaga (Eleginus navaga Pall.), polar cod (Boreogadus saida Lepechin) and arctic flounder (Liopsetta glacialis Pall.) in the laboratory. Aquaculiure 6 233-242. BARANENKOVA, A. S., PONOMARENKO, V. P. &

KHOKHLINA, N. S. (1964): Distribution, sizes and growth of larvae and fry of polar cod (Boreogadus saida Lepechin) in the Barents Sea. Int. Coun. Expl. Sea Gadoid Fish Comm. Rep. No. 96: 1-15. BOWER, C. E. (1983): The basic marine aquarium. Springfield IL: Charles C. Thomas. BRADSTREET, M. S. W.. FINLEY, K. J., SEKERAK, A. D., GRIFFITHS, W. B., EVANS, C. R., FABIAN, M. F. & STAUARD, H. E. (1986): Aspects of the biology of arctic cod (Boreogadus saida) and its importance in Arctic marine food chains. Can. tech. Rep. Fish. Aquat. Sci. No. 1491: 1-193. CRAIG, P. C., GRIFFITHS, W. B., HALDORSON, L. &

MCELDERRY, H. (1982): Ecological studies of arctic cod Boreogadus saida) in Beaufort Sea coastal waters, Alaska. Can. J. Fish. Aquar. Sei. 3 9 395406. HOLETON, G. F. (1974): Metabolic cold adaptation of polar fish: fact or artefact? Physiol. 2001. 41:

RASS, T. S. (1968): Spawning and development of polar cod. Rapp. P.-v. R i m . Cons. perm. int. Explor. Mer. 158 135-137. SAMEOTO, D. (1984): Review of current information on arctic cod (Boreogadus saida Lepechin) and bibliography. Dept. of Fisheries and Oceans, Ocean Sciencific Survey Atlantic, Bedford Instititute of Oceanography.

137-152.

Manuscript submitted 2 September 1991