YOU AT^. 1971. Effect of feeding coho salmon and other Great Lakes fish on mink reproduction. Can. J. Zool. 49: 61 1-616.Feeding experiments were conducted to investigate reproductive problems attributed to the feeding of Great Lakes coho salmon to mink. Several other s p i e s of fish were fed for comparison. Whole, raw, sexually mature coho salmon taken from tributarie!: of Lake Michigan were pound, m~xed into a diet at a 30% level, and fed to mink before breeding and during gestation. This diet causcd reproductive failure and (or) very early kit mortality. Feeding canning by-products of coho salmon from the same source and at the same level to adult mink for 3 nlonlhs resulted in mortal~ly. Reduced reproductrve performance and (or) excessive kit mortality were oljserved in mink which were fed d~ets that contmned Lake Michigan bloater chub, Lake Michigan yellow perch, and mature coho from the e k e Erje system. Mink rations which contained West Coast coho salmon and Lake Erie yellow perch dld not Impau reproduction nor result in excessive mortality.No correlation was found between the degree of oxidative rancidity or mercury contamination of the fish and the reproductive performance of the mink. The levels of pesticide residues in the fish (and the complete diets) and the degree of reproductive decline and (or) kit mortal~ty observed in the mink appeared related.The study demonstrated that coho salmon per se does not cause the reproduction and mortality problems. Further, the disorder is also associated with other species of Great Lakes fish and appears to be dependent upon the species of fish and its environment.

Concentrations of DDT residues were highest in parts of the body with the highest oil content in four species of fish from Lake Michigan: yellow perch (Perca flavescens), bloater (Coregonus hoyi), lake trout (Salvelinus namaycush), and coho salmon (Oncorhynchus kisutch). Dressing reduced the DDT residues and oil content by more than 90% in yellow perch but had little effect in the other three species. The concentration of DDT residues in bloaters was changed little by smoking but was reduced 64–72% by other methods of cooking: from 8.0 ppm (raw) to 2.2 ppm after frying in corn oil; from 10.7 to 3.9 ppm after frying in lard; and from 9.1 to 3.2 ppm after broiling. The concentration of DDT residues in fillets of yellow perch changed only from 0.3 ppm (raw) to 0.4 or 0.5 ppm after baking, frying, or broiling.

No abstract

Fishery products preserved by freezing potentially have characteristics more like those of fresh fish than do products preserved by any other process currently in use. Despite the widespread acceptance of frozen fishery products, however, a decided consumer preference for fresh fish often exists. The reasons for this preference may be attributed to a progressive deterioration in quality of the frozen product, particularly after prolonged cold storage. When fish muscle is frozen and subsequently thawed, a cloudy, liquid phase called drip exudes from the muscle. In addition, when the thawed muscle is cooked, the surface of the cooked flesh often is coated with an unsightly white deposit of coagulated drip proteins, commonly referred to as curd. Further, the thawed fish when cooked often toughens and becomes fibrous as compared with cooked fish that has never been frozen. The rate of quality deterioration in frozen fish is related not only to cold storage conditions but also to species differences.Several different theories have been proposed concerning the origin of drip in frozen fish,muscle and reviews dealing with this problem and factors influencing the production of drip have been discussed elsewhere (3, 7). The most recent evidence (7,14,17). however, would suggest that drip is due to denaturation of proteins which normally tend to hold the water of the muscle and to changes in the cellular structure of the muscle brought about by the formation of ice. The general effect of freezing and the rate of freezing on the fine structure of fish muscle has been demonstrated by histological techniques, although experimental findings often appear rather contradictory.Love (10) recently has suggested that the appearance of desoxypentosenucleic acid (DNA) in the expressible fluid from thawed muscle indicates rupture of the cell membrane, with liberation of nuclear material.The fact that disintegrated fresh tissue does not liberate an appreciable quantity of muscle juice, however, would suggest that the mere rupture of the cell membrane in itself does not fully explain the release of large quantities of drip when the same material is frozen and thawed. It has been demonstrated (14) that the retention of cellular fluids or drip is related to the power of muscle proteins to imbibe free liquid. This imbibing power is influenced by electrolyte content and by pH and a zone of minimum effect is exhibited in the regions of the isoelectric points of the fish muscle proteins (27). The aggregation or loss of solubility of actomyosin-the principal contractile protein of the myofibril-by freezing, and its subsequent inability to rehydrate has been demonstrated by many workers ( 6 ) . Dyer (6) reports that the sarcoplasmic or non-contractile proteins, however, show no change of solubility on freezing except after very long storage. The denaturation of the contractile proteins was also suggested by Mahadevan and Carter (12), who detected a permanent and constant decrease in volume of fish flesh after freezing and thawing. Salt dehydrati...

Following the current trend in food preservation, fishery products are being prepared and sold in the frozen state in increasing quantity each year. It is well known, however, that a decided consumer preference for fresh fish to frozen fish exists in many areas, despite the convenience of the frozen product. The reasons for this preference have been well recognized and have been the basis for extensive study throughout the world for many years.The important changes (2) in fishery products that have been associated with freezing and cold storage are loss of tenderness and charactcristic fresh-fish flavor. There is a subsequent development of texture changes-variously described as toughness, stringiness, mushiness, etc.-and of off-flavors and off-odors. Development of off-flavors and -odors is nsually attributed to fat oxidation, even in lean fish. Loss of characteristic fresh-fish texture has been related to what is termed protein deiiatnration or, more simply, alteration.Protein denaturation may be caused by many agents or conditions and, in effect, may result in a product of quite variable quality. '3' ince relatively little is known concerning the true natiire or structure of proteins, denaturation and its over-all effect on the quality of a food product is also iiicoinpletely understood at the present time.Attempting to develop more objective methods for the measurement of frozen fish quality, Reay and Kuchel (6) applied to fish a procedure earlier used in classical studies on the proteins of rabbit muscle. Reay foaiid a decrease in the solubility of the muscle proteins in salt solutions after frozen storage of the fish and drew attention ( 7 ) to the denaturation phenomenon. On further investigation, Canadian workers ( 3 ) showed that it was the protein fract,ion called actomyosin which was denatured.Tlic non-actomyosin fractions remained unchanged except after very long storage. I n combination with taste panel testing, it has been shown (2) that the solubility of actomyosin appears t o parallel and to anticipate chaiiges in texture and flavor, thus providing a measure of the quality of a particular sample of fish.This paper reports a study of changes in properties of the actomyosin fraction of fish muscle that has been subjected to frozen storage. The propertics of chemical activity, asymmetry, and solubility of the protein were imestigated. An attempt has been made to gain a better nnderstanding of the basic nature of the adverse effects of freezing and cold storage on the quality of fish protein.EXPERIMENTAL Materials and methods. All of the experiments reported in this paper were carried out on actomyosiii isolated from the muscular tissue of yellow-striped rorkfish (Scbasiodes nebulosus). 505