No B. Braaten

Transcription

1 4 ISSN Canadian Translation of Fisheries and Aquatic Sciences No Status and future prospects: cod and other marine fish as industrial products B. Braaten Original title: Status og fremtidsutsikter: torsk og annen havfisk som industrivare In: Fisk. Gang 69(10): , 1983 Original language: Norwegian Available from: Canada Institute for Scientific and Technical Information National Research Council Ottawa, Ontario, Canada KlA typescript pages

2 1* Secretary Secrétariatt of State d'état MULTILINGUAL SERVICES DIVISION DIVISION DES SERVICES MULTILINGUES TRANSLATION BUREAU BUREAU DES TRADUCTIONS Translated from - Traduction de Norwegian Author - Auteur Bjorn Braaten Title in English or French - Titre anglais ou français Into - En English c.tra5 5 û Status and Future Prospects: Cod and other Marine Fish as Industrial Products. Title in foreign language (Transliterate foreign characters) Titre en langue étrangère (Transcrire en caractères romains) Status og fremtidsutsikter: Torsk og annen havfisk som industrivare. Reference in foreign language (Name of book or publication) in full, transliterate foreign characters. Référence en langue étrangère (Nom du livre ou publication), au complet, transcrire en caractères romains. Fiskets Gang LIBRARY IDENTIFICATION FICHE SIGNALÉTIQUE Reference in English or French - Référence en anglais ou français Progress of Fisheriee Publisher - Editeur Place of Publication Lieu de publication Directorate of Fisheries Year Année DATE OF PUBLICATION DATE DE PUBLICATION Volume Bergen, Norway D2 Issue No. Numéro 10 Page Numbers in original Numéros des pages dans l'original 263 " 269 Number of typed pages Nombre de pages dactylographiées 1-21 Requesting Department Ministère-Client DFO C. Ter', Liete." 4 Trans ation ureau No. Notre dossier - no - 1', l2'ï 373l Branch or Division Direction ou Division îles Translation (Initials) Traducteur (Initiales) Person requesting Demandé par A ra;-, : Your Number Votre dossier no Date of Request Date de la demande c17, î3 Canacrâ SEC 5411 (Rev.82/11)

3 141 Secretary Secrétariat of State d'état MULTILINGUAL SERVICES DIVISION DIVISION DES SERVICES MULTILINGUES TRANSLATION BUREAU BUREAU DES TRADUCTIONS Client's No. No du client Department Ministère Division/Branch Division/Direction City Ville, I) Fo I eb, Bureau No. No du bureau Language Longue Translator (Initials) Traducteur (Initiales) Q ef eertue_ci ta ri I / f Ill/, Status and Future Prospects: Cod and other Marine Fish as Industrial Products. (Status og fremtidsutsikter: Torsk og annen havfisk som' industrivare) by Bern Braaten, Institute for Marine Biology, Aquaculture station Austevoll Fiskets Gang, no 10, p Large changes are taking place in the Norwegian fishing industry. A few years ago aquaculture was a foreign word that few people knew anything about. Today Norwegianfarmed salmon and rainbow trout are known as quality products all over the western world. But how about our other fish species such as cod and pollock, or the more exotic flat fishes like halibut, European turbot and Dover sole? Even if developments are in the early stages, a revolution can occur rapidly with one or more of these species, shouid we so desire. p. 263 Canadâ SEC 5-25 (Rev. 82/11)

4 2. It should be clear to everyone that Norway has very special,çonditions for carrying out aquaculture on a large scale. Few countries, if any at all, have better opportunities. We have a coastline of 53,000 km counting all our 22,000 islands. For a country located so far north, we have very favorable water temperatures thanks to the warm waters from the Atlantic Current. We must go south of Jaeren before the seawater drops below the freezing point in the winter, and even in the far north there is open water and possibilities for survival the year around. At least asimportant as clean seawater is the availability of inexpensive raw material for feed. Intensive fish farming requires large amounts of proteins and fats which preferably should come from marine products since this is close to the natural food of the fish farmed. Which species besides salmon and rainbow trout are of current interest for farming today and in the near future? Even if this question cannot be fully answered today, we have good informationiboth\fromithismuntry and abroad that the choice is between four or five species. In order for a species to be successfully farmed, certain requirements must be fulfilled which can be briefly outlined as follows: 1. The species must be able to live, grow, develop, and thrive under our environmental conditions.

5 3. 2. The species must be able to reproduce in captivity, and the whole life-cycle including hatching, first feeding, sexual maturi'ty and spawning should be possible to be carried out under culture. 3. It must be profitable to carry out farming of the species. Flat fishes. Of the marine species, flatfishes naturally stand out since many of them are highly prized food fish which achieve high priceslbothçue -Ithe domestic and export markets. How do flatfish species fit into the criteria established? Plaice is common along the whole Norwegian coast and thrive well in our waters. In Great Britain, research over many years has resulted in a farming technology which makes mass farming possible but not profitable. In Norway the plaice is not very interesting for intensive rearing, since not much is consumed and it has a relatively low market value. However, in the long term it could prove possible to farm this species. Fig. 1 A comparison of growth experiments with European turbot in warm water and in cold water. The warm water experiments were carried oat at the State Biological Station, Flbdevigen near Arendal (D. Danilssen) and those with varying temperatures ( C) at the Aquaculture Station Austevoll, south of Bergen.

6 ILI > 600 FLODEVIGEN C I- f. AUSTEVOLL 5-15 c." DAGER e. European turbot and Dover sole are both high-priced species in Europe. Commercial farming trials with both species are being carried out in Great Britain and France. Turbot is found along the Norwegian coast up to Trondheim but is rare further north. Dover sole is most numerous in the southern part of the North Sea and is rare north of Stavanger. Both species require warm water to be of interest in intensive rearing. In Norway the species are only of interest if there is a reasonable supply of warm water, preferably the year round. Both are known as difficult species to start feeding; eggs have a diameter of mm

7 5. and larvae are about 3 mm long. The larvae require live zooplankton in the start-feeding phase. Sole can be started off on newly hatched brine shrimp Artemia, and later fed r bristle_ wormsbefore going to a weaning period with artificial feed (1). Sole grows well at té:mperatures. from 14 to 240 C but prefers 20 C, and researchers at the White Fish Authority feel that it is possible to produce a 250-gram fish in 1-1 years. European turbot is very difficult to start feeding and require5 wheel animals ( Rotifers ) as a starting feed together with unicellular algae (3). Gradually the feed is changed to newly hatched brine shrimp and finally weaning over a week to artificial feed. In Scotland ) 50-g turbot are transferred to floating enclosures in the sea when the temperature is 10 C. Over a period of 30 months they grow to 500 grams and market-size (4). It is assumed that it is possible to produce 2-kg fish after 2-2j- years at C. France seems to concentrate mostly on turbot and is so far not counting on profitable cultivation of sole. In Great Britain commercial work is being carried out with both species. Scattered experiments have also been carried out in Norway, and at the State Biological Station at Flodevigen, Arendal, sole spawn was easy to hatch. Best growth was achieved at 210 c, but there were problems with mortality. After 18 months the sole had grown to about 100 grams.

8 Parallel trials in Austevoll and Flodevigen further confirm that,rearing of turbot must be carried out in warm water (fig. 1). In Flnodevigen the turbot grew to 1.4 kg after 21 years at C ; while the same group was not quite 200 grams at However, further experiments should be carried out with turbot to be fed initially in warm water and then transferred to net enclosures in the sea in May/June. Halibut can be the new fish species for farming if success is obtadned with keeping broodstock $ hatching and initial feeding. It has rapid growth and thrives in our cold waters. Norwegian researchers managed in 1980 for the first time to feed larvae up to metamorphosis. This year broodstock fish are being cultured in Askôy near Bergen where the Institute for Marine Research collaborateywith Mowi A/S and Norwegian Hydro. Trials with eggs and laryae are to be carried out at Austevoll and Fl8devigen. It is hoped that work with halibut will finally get underway in earnest, a species we know little about but have great expectations for. Even if the flatfishes represent the most expensive and best recognized food fishes, it is another species, namely cod, that has received the greatest attention by researchers here in Norway. This is because cod is one of the most

9 important fish species both with respect to and popularity e * with most Norwegians. fishery If we can master cod rearing ) we can deal successfully with almost any species, and it is the initial feeding of the larvae that is the critical and most difficult phase. The cod larvae are less than 4 mm long at hatching and normally live ogthe younger stages of red copepod (Calanus sp.),,one of the most important forage animals in the sea. These small animals are difficult to obtain alive in large quantities ) and other solutions are therefore sought, such as cultivation of wheel animals ( Pc1 fra ) or introduction of artificial feed (18,19). p. 26 At the Aquaculture Station Austevoll, work has been carried out for several years with two different techniques for the mass production of cod larvae. The experiments are being supported by Elf Aquitaine Norge A/S. One method involves the rearing of larvae in large tarpaulin (canvas) bags supplied with zooplankton. The collection of plankton is being carried ait by pumping seawater through large plankton nets with the help of pumps. By regulating the mesh size in the plankton net, animals of desired size can bp filtered out. The plankton is collected in a small net box and then pumped over to the tarpaulin bags. In the other method newly hatched larvae are placed in a closed off seawater pond with a narrow inlet which is

10 8. being supplied contiikusly with fresh bottom water by a powerful submersible centrifugal pump. (21) All natural enemies are first removed from the pond by rotenone treatment, and the cod larvae live off the plankton produced naturally in the pond. For both systems it is important to develop an artificial feed after metamorphosis when the larvae are 12 mm long. There is good hope that one or both methods should be able to produce large quantities of cod fry in the near future. The primary purpose of the studies has been the production of viable fry for stocking in order to support local stocks of cod. Earlier studies at Flodevigen and in 1982/83 at the Aquaculture Station Austevoll have shown that the released fish are very stationary. By using sonic tags it has been determined that the fish have remained in the same area for several months. The experiments are important also in other respects. Today cod seems to move up as a new species for intensive p. 26( rearing. As of January 1983, the Directorate of Fisheries had received 115 applications for licences to rear cod (Table I). The applications are distributed over 11 counties-with most coming from Nordland and Nord TAndelag. Not a single license has so far been issued ) although many have started experimental operations. Farmers are dependent on purchasing trap-caught small cod or gillnet/purse seine-caught fish that

11 9. are not injured. Many fishermen feel that this is a threat to the coastal cod stocks. The time has come for a new thinking of how these coastal stocks can best be utilized. In quota negotiations with the Soviet Union, Norway has been allocated 40,000 tonnes extra for coastal cod. It is uncertain if this is a. correct estimate for the Norwegian coastal cod stocks. wornismodning sexual maturitz, spawning growth (gram re bum nøt encllosur STORE KKR arge tan g"liatching KAR 44 vessel KLEKKUIG OSE pondr bag 4 rortra. 1 ""0.., POLL I feed factor Anta II rand. number of month: Fig. 2. Growth of coastal cod from hatching to spawning. The curve is drawn from a number of different experiments and must be considered one of many possible growth curves for cod which are reared like salmon and rainbow trout. Cod larger than 50 grains is fed capelin.

12 10. SOKNAD OM KONSESJON PA TORSK TabeII I Applications for licenses to rear cod. lnformasjon fra Fiskerldirektoratet Information from Directorate of Fisheries Volum (sokt) m3 Antall soknader Volume Wu (appiiiits6, for) 4 applications ** (350000) 18 +1** Fee County Aust-Agder Vest-Agder Telemark Rogaland Hordaland Sogn og Fjordane More og Romsdal Sor Trondelag Nord-Trondelag Nordland Troms * avstengt omràde ** Uspesitiserte sokere med hensyn til volum *350,000 closed off area **Non-specific with respect to volume ** ** The Institute for Marine Research calculates that twice as much coastal cod is caught from Stad to Lofoten as in the rest of the country. The stocks in Southern Norway have not been studied extensively. The license applications represent a rearing volume of over 1 mill. m 3 p Totatt but it will take some time to fill this quota. In large parts of the country the coastal cod is lightly exploited, and trapping of stocking fish could represent a rational utilization of resources. For other parts of the coast with a well developed coastal fishery, increased exploitation could affect the spawning stock. If an intensive cod rearing industry will develop,

13 J1. new production units for stocking fish should be established. It is known from trials in Austevoll that it is possible to Ifroduce cod with a weight of about 2 kg in 22 months after hatching (fig.2). In these experiments wild fish were reared until they spawned naturally. The eggs were incubated in the laboratory and the larvae set out in bags or a pond for feeding. Fish have been reared both in tanks ashore and in fine-mesh floating enclosures. Larvae from 1981 have today become sexually mature fish of kg. A weight loss of up to 25% can be expected after spawning. The growth potential is great and among the fish farmers in Mâlôy and Èôrvik, weight gains from O.L to 3 kg in 9-14 months have been registered. Most cod farmers start with fish near 0.5 kg caught in spring or fall and sold before Christmas the same or following year. Coastal cod mature early, and first-time spawners weighing under 0.5 kg have been found. The feeding habits of cod are different from those of salmon in that they eat larger meals and more seldom. Experience has shown that cod over 300 grams can be fe:d every second day, and large cod especially seem to have better growth and feed utilization when there, are longer intervals between feedings than when feeding one or several times per day. Cod seem generally to utilize the feed well, and in controlled experiments the calnulated feed consumption

14 12. was kg capelin per kg weight gain (net weight). Practical experiments by farmers indicate values of 4 kg wet feed per kg growth. According to information from fish farmersthe cod seem to thrive well in densities of 40 kg/m3. There is still not enough information available to recommend number of fish per unit of space. Problems include relatively large losses that can still not be fully explained. It could be due to natural causes such as difficulties in counting fish when transferring from well-boats. Cannibalism is a pronounced phenomenom in fry and 0-group fish but is probably not a problem with large fish being fed regularly. Cod can get vibriosis of the type demonstrated in pollock. Large losses of small fish have occurred in the summertime as a result of sudden outbreaks of vibriosis. The antibiotics commonly used for salmonids do not seem to be effective on cod. The development of cod rearing will to a large extent be dependent on the selling price of the product. Profitable operation is dependent on the supply of inexpensive raw materials for feed and utilization of unused capacity in installations that normally rear salmonids.

15 13. Quality of Marine Fish From "wild" fish, and especially cod, the most important quality criteria that affect marine-fish are known, thanks to studies by Dr. Robert Malcolm Love at Torry Research Station in Aberdeen. The cod studies that Love describesin his book "Chemical Biology of Fishes", Vol. 2 ) include data on wild fish caught in different geographical areas throughout the year, together with followup aquarium experiments. In addition, a large number of published papers have been thoroughly and critically evaluated. In the rearing of marine fish the experiences and conclusions that Love has reached will be of great importance for best possible utilization of the product. In intensive culture the fish rearer has full control over the fish. He can supply the required quantity and quality of feed and also harvest the fish at a favorable time with respect to flesh quality, time of year, price and market. Some of Love's studies and conclusions and the consequences these have for the rearing of marine fish will be discussed in the following. Love has primarily evaluated the following quality criteria that govern the use of fish as food; taste, odor, texture (in the mouth after cooking), color, surfi.cial structure and appearance of the fish muscle.

16 1 :1 14. All characteristics can be said to vary with respect to it time of year, time of catch, spawning cycle, current conditions and local variations in feed supply. Genetic variations seldom seem to play a role except for color variations in the skin and the ability to produce antifreeze fluids in the blood at low temperatures (7). Taste and Odor When fish is frozen, it will gradually develop a characteristic taste and odor that can remind one cf cardboard, cold tea or fishmeal. This rancidity process is well known in the storage of fatty fish like herring and salmonids, but also in lean fish where there is almost no fat, unpleasant odors and taste can develop. The reason is oxidation of unsaturated fatty acids in the phospholipids. In lean fish like cod, almost all muscle lipids consist of phospholipids. Love showed that it is the phospholipid part that varies from place to place throughout the year and not the neutral lipids. Ross and Love (8) carried out a starvation experiment with cod for 2 months and froze the fish together with a control group that had been fed. After thawing and cooking the control group had a faint "freezer" taste and odor while the starved group largely was fine with a good taste. According to McGill (9), it is cis heptenal that is responsible for the unpleasant taste. Love (5) concludes

17 that odor and taste in lean fish that is frozen will be subject to seasonal variations according to the degree of starvation the fish is exposed to. Love further claims that C22:6 is the mostimportant fatty acid and the_most unsaturated, and that the amount decreases steadily when fish are starved. This is in accordance with a reduced 15. formation of cis heptenal in starved frozen fish. This means in practice that farmed fish that are fed regularly throughout the year will not be very suitable as a frozen product. Texture There is a close relationship between the texture of cooked fish muscle and ph measured after the fish is dead (10). According to Love and co-workers (11) ) the texture showed a high negative correlation with ph (fig 3). The fish muscle became tougher with falling ph, and this be effect was so pronounced that fish toaused for freezing and cold storage, something that makes the muscle even tougher, should not have a ph lower than (12). As long as the fish is alive ) muscle will be neutral. ph in the fish When the fish dies the muscle eycogen is broken down anae-"robically to lactic acid ) and the ph drops. At 0 0 C it takes 15 hours before the ph has reached a minimum value (13). Fish in poor condition will have little glycogen in the muscle and ph will remain near neutral after death. Farmed cod ) which will normally

18 have a very good nutritional status the whole year ) therefore be expected to have a low ph after slaughter../ These fish will therefore not be very suitable for freezing and storage and should be. marketed fresh. Appearance The appearance of the fish will always bear is importance for the buyer regardless of if ii-ysold live, gutted or in fillet form. can It should have correct shape and coloration and be without wounds and parasites. For farmed salmon and rainbow trout clear criteria for how the product should be have gradually developed. Marine species such as cod and pollock will easily take on an atypical appearance when reared as a result of overfeeding. The liver grows large and the fish looks like it has a swollen stomachras if it is about to spawn. Love (5) has also shown that at low muscle ph ) the fillet will split open (gape). This is explained by the fact that the fillet consists of muscle blocks held together with connective tissue. This tissue is very sensitive towards small changes in ph. The mechanical strength at ph 7.1 is four times greater than at ph 6.2 (14). The buyer will also evaluate the color of the product after cooking. but fish have both light and dark muscle. Cod muscle is expected to be white, 16. It is assumed that dark muscle is used mostly at low swimming speeds and that the color becomes more intense at increased activity (5).

19 1 7. Color changes in muscle vary with the season and fish migrations. n farming it is to a certain degree possible to regulate the activity of the fish and thereby also the pigmentation of dark muscle. Muscle Water Content When cod starve,the water content of the white muscle is increased, and the yearly maximum coincides with the spawning time or shortly afterwards (15). In aquarium experiments where cod were starved ) there was a considerable delay before the water content increased (fig 4). (15). Under such conditions the cod will first use fat from the liver and then muscle protein when the fat is almost used up. When protein is used it will be replaced with water. Love found that immature cod had the same water content all the time with the exception of a small peak in March. First-time spawners had an increased water content and used longer time to recover. The largest codsthat had spawned earlier had the highest water content at spawning (fig 5). When the muscles take up water ) there is a change in the water - ion - protein balance and the jellylike muscle becomes whitish and loses transparency. This color intensity varies throughout the year and follows spawning season. Usually a muscle that has the normal bluish transparency will be preferred to a pale white color. By slaughtering the farmed cod before the spawning period, tish with high water content and whitish muscle can be avoided.

20 18. In plaice ) Hume and co-workers (16) demonstrated several differences in the minor components of the muscle by comparing trawl caught fish with reared fish. In farmed fish ) both skin and muscle had a tendency to be darker, and this was especially typical around the bloodvessels that had become darker because of melanin deposits (17). We are still in the starting phase of rearing of marine fish and it is today difficult to evaluate the demand for such products. All fish produced must have a market that is willing to receive the product at a price that makes it profitable for the farmer. The reared products are different from wild fish and the quality of the product can to a considerable degree be determined by the farmer. of the most important conditions will therefore be to obtain as much information on farmed fish as possible, not about th onliological data but also about the product the buyer will be paying for. One

21 19. REFERENCES REFERANSER 1. White Fish Authority Dover sole is ready for the fish farm. Fish Farmer 3 (2) White Fish Authority All out to bring Dover sole to the farm. Fish armer 3 (3) HoWell, B Turbot set to take off as larvae supplies improve. Fish Farmer 2 (3) White Fish Authority Turbot gets boost ton Scottlands West Cost. Fish Farmer / (6). 5. Love, R.M The chemical Biology of fishes Vol Love, R.M Colour stability in cod (Gadus morhua L) from different grounds I. Cons. perm. int. Explor. Mer Duman, I.G. og De Vries, A.L The effects of temperature and pho- toperiod on antifreezeproduction in cold water fishes. J.ecp.zool Ross, D.A. cg Love, R.M Decrease in the cold store flavour developed by frozen fillets of starved cod (Gadus morhua L) J. Food Technol McGill, A.S An investigation into the chemical composition og the cold storage flavour components of cod. 1FST mini-symposium on freezing. Institute of Food Science and Technology. U.K.: Cowie, W.P. og Little, W.T The relationship between the toughness og cod stored at -29'C and its muscle protein solubility and ph. J. Food Technol. 1, : Love, AM., Robertson, I., Smith, G. og Whittle, K.J The texture of cod muscle. J. Texture Stud. 5: Kelly, K.O Factors affecting the texture of frozen fish. In "Freezing and Irradiation of Fish" (Ed. Kreuzer, R.), pp Fishing News (Books) Ltd., London. 13. MacCallum W.A., Jaffrey, J.I., Churchill, D.N., Idler, D.R. og Odense, P.H Postmortem physic chemical changes in unfrozen Newfoundland trap-c.aught cod. J. Fish. Res. Bd. Can. 24: Love, R.M., Levity, I. cg Garda. N.G The connective tissues of fish VI. Mechanical studies on isolated myocommata. J. Food Technol. 7: Love, R.M "The chemical Biology of Fishes". Vol. I Academic Press, London and New York. 16. Hume, A.H., Farmer, I.W. og Burt, J.R A comparison of the flavours of farmed and trawled plaice. J. Food Technol. 7: Love, R.M., og Hume, A.H The quality of farmed products. Fish Farm Int Huse, I. Gokstad, S.L., Gray, T., Jensen, P., Kristiansen, A. oo Opstad, I Present status of an intensive cod-rearing experiment at Austevoll, Norway. Coun. Meet. int. Coun. Explot. Sea F:16: Huse, I An attempt to start feed cod larvae with artificial diets. Coun. Meet. int. Coun. Explor. Sea. F:14: Huse, I. cg Jensen, P.A Status of an intensive cod rearing project in Norway Coun. Meet. int. Coun Explor. Sea. F:23: Oiestad, V. og Kvenseth, P.G Large-scale rearing of cod fry (Gadus Madura) in an inlet. Coun. Meet. Int. Coun. Explor. Sea F:23: Braaten, B Fordoyelse/emarring hos torsk Delprosjekt B: Energiomsetning og vekst. Sluttrapport NFFR Prosjekt - NFFR I : 54 pp. 22_ Braaten, B Digestion/nutrition of cod Part project B: Energy Conversion & growth. Final report NFFR, Project r,nffr ;54 PP.

22 20. 6 Texture OS-. ti '., ".:st...,1... es:. «8 I en4. -,...e. le. U)..0,_ z, _ ).. '.:. s '.s. o - be... e A-..._ -.. % : 1 I I l A- I I f ph. Fig 3. The effect of post-mortem ph on the texture of cooked cod muscle when eaten. The muscle water content varied from 80 to 89%. Texture over 3 means firm or tough samples, under 3 soft. From: Love, Robertson et al.(1974). J Water content, muscle 0 tat 0 r. ss s,, \ VANN water go A 6. 0 <so SULTPERIODE UKER Starving period, weeks Fig. 4 Water content and ph in muscle of cod starved at 90 C; from Love (1979).

23 21. /7 water content muscle e Z 81 r ist plia"wn e-gaenderseveral times fbrstegangsgyter first time spawnqr 80 NOV JAN MAR MAI JUL SEP Fig. 5 Water content in muscle of cod from Aberdeen Bank in (Love 1970)