摘要:

On the basis of some of the recent modifications of Dyer's colorimetric test for measuring trimethylamine (TMA) in fish, a procedure is described that gives both the TMA and the dimethylamine (DMA) contents. Measurements on 84 frozen-stored fillets of haddock, cod, pollock, cusk, and hake showed a correlation coefficient of 0.94 between DMA values obtained by the copper–dithiocarbamate test and those obtained by the picric acid procedure. The simultaneous measurements of TMA and DMA are useful in estimating the quality of frozen-stored gadoid fillets, the TMA value indicating the extent of microbial spoilage before the muscle was frozen and the DMA value the extent of deterioration through action of tissue enzymes during frozen storage.

ISSN:0706-652X    

DOI:10.1139/f74-065

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Rates of light-saturated division ofThalassiosira fluviatilisandIsochrysissp., marine unicellular algae, were regulated by temperature and daylength at 25 C, and primarily by temperature at 20 C or less. The rates forChroomonas salinaappeared to be regulated by temperature and daylength at temperatures between 10 and 25 C, with maximum effects of daylength occurring at temperatures of 20 and 25 C. Physiological mechanisms through which temperature and daylength interact to regulate division rates of unicellular algae are discussed.

ISSN:0706-652X    

DOI:10.1139/f74-066

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The presence of infectious pancreatic necrosis (IPN) virus in brook (Salvelinus fontinalis) and rainbow (Salmo gairdneri) trout was identified and further investigated. A high incidence of virus was found by virological examination of kidney tissue from yearling and older trout. By comparison, brook trout had a much higher incidence of virus than rainbow trout.The virus was isolated most frequently from the kidneys of both species of trout. These findings indicate that the examinations of peritoneal washes and feces is not adequate for the detection of IPN carrier fish.

ISSN:0706-652X    

DOI:10.1139/f74-067

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The oystersCrassostrea virginicaandOstrea edulisfrom a common habitat showed species-oriented fatty acid composition patterns for total lipids and lipid fractions. Attempts to modify these patterns by offering the unicellular algaeDicrateria inornataandIsochrysis galbanaas food suggest that the oysters rapidly convert qualitatively or quantitatively unusual fatty acids to these species-oriented compositions, although only in the combination ofD.inornataandO.eduliswas enough fatty acid taken up to modify the oyster fatty acid composition in an easily detectable way. The unusual C22nonmethylene-interrupted diunsaturated fatty acid components were not found in theO.edulisused for this study.

ISSN:0706-652X    

DOI:10.1139/f74-068

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Trapnet catches of northern squawfish (Ptychocheilus oregonensis) at Griffen and Cultus lakes, British Columbia, indicated peak activity and feeding in the twilight and dark hours. At Griffen Lake, squawfish force-fed 2.0 g of redside shiner (Richardsonius balteatus), and held at 17–20 C, digested at a rate of roughly 14%/h. At Cultus Lake, squawfish trapped during the peak of feeding activity, and held at 10–12 C, were sacrificed at 6-h intervals, and showed a digestion rate of sockeye salmon (Oncorhynchus nerka) smolts of 14%/h. Larger fish ate larger volumes of food. Regression techniques are not completely adequate for describing the course of digestion, which apparently involves an initial period of retention of food, followed by a fairly rapid evacuation of most of the ingested material. Most fish cleared their stomach contents in 24 h, and one half had done so between 12 and 18 h. In the laboratory, squawfish force-fed rainbow trout (Salmo gairdneri) had rates of digestion which increased with temperature, from about 5%/h at 4–6 C, to 40–50%/h at 24 C. Larger weights of food were digested at slower rates, but there were no consistent differences in rate of digestion by different sizes of squawfish.The rates of digestion are higher than those reported for various predatory European fishes.

ISSN:0706-652X    

DOI:10.1139/f74-069

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

In a small, shallow beaver pond near Georgian Bay, Ontario, life histories of each of the three limnetic copepods found were basically similar in the 3 yr 1970–72 although the patterns were occasionally obscured.Cyclops bicuspidatus thomasipresumably emerged from diapause at stage C 4 when the ice broke and went through one complete cycle to C 4 in 3–4 wk, reentering diapause in late spring.Mesocyclops edaxemerged from diapause at C 4 slightly later in spring and underwent four complete cycles, reentering diapause in midautumn; normal time to complete a generation was about 1 mo.Diaptomus reighardihatched from resting eggs in early May and produced four complete generations, the last maturing in early autumn; development of spring and summer generations required 1 mo and that of autumn generations about mo. During 1972 lowered water levels resulted in increased heat content of the pond per unit volume and this was reflected in some acceleration of development rates ofM.edaxandD.reighardi. At most sampling timesM.edaxhad about double the fecundity ofD.reighardiindicating a correspondingly high mortality rate that might be the result of lower egg viability, cannibalism, or competition between nauplii of the two species.

ISSN:0706-652X    

DOI:10.1139/f74-070

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Of anadromous Dolly Varden (Salvelinus malma) migrating from the sea into Hood Bay Creek, Admiralty Island, and two other nonlake streams nearby, 61–87% were immature. Most of the immature fish left the streams within a few days of entering. Though nearly all smolts leaving the creek for 3 yr were marked, only 16–21% of the immature fish entering the stream bore these marks. Many of the fish marked in the creek as smolt were recovered entering the two other study streams as immature fish but not as spawners.Mature immigrants remained in the streams for several weeks until they had completed spawning in October and November. Most Dolly Varden that spawned in the creek had been marked there previously as smolt or as spawners, and none were observed to spawn in a stream other than the stream of origin. Smolts transplanted during their oceanward migration returned to spawn in the receiving stream, and adults displaced to saltwater sites on returning to the study streams returned to their home streams. Most fish from the creek spawned only once or twice. Males suffered a much higher spawning mortality than did females.This study and others on fish from lake-stream systems suggest that (1) anadromous Dolly Varden from nonlake streams in southeastern Alaska migrate both between nonlake streams and between nonlake streams and lake-stream systems; (2) during their first summer in the sea, fish from nonlake streams enter several streams while searching for one with a lake; (3) mature fish from nonlake streams leave their wintering area, usually a lake, and return to their home streams to spawn; and (4) mature fish from lake-stream systems go to the ocean to feed for several weeks to a few months and return to their home system to spawn and overwinter.

ISSN:0706-652X    

DOI:10.1139/f74-071

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Arylamidase activity in muscle extracts of mackerel, mullet, whiting, blue crab, quahog clam, and shrimp was investigated. The optimumpH for activity was between 7.0 and 7.5 for each species using alanyl-β-naphthylamide as substrate. Enzymes of the three species of fish exhibited maximum activity against alanyl-β-naphthylamide, whereas the clam showed maximum activity with leucyl-β-naphthylamide and the crab and shrimp with lysyl-β-naphthylamide. Puromycin inhibited each of the arylamidases. Acrylamide gel electrophoresis of the crude extracts suggested the presence of one arylamidase in muscle of the fish, crab, and clam. The shrimp muscle extract contained two active enzymes. Upon electrophoresis, the faster moving enzyme from shrimp muscle was active against lysyl-, alanyl-, and leucyl-β-naphthylamides, but the slower moving enzyme was active only against lysyl-β-naphthylamide.

ISSN:0706-652X    

DOI:10.1139/f74-072

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Exposure of brook trout (Salvelinus fontinalis) to sublethal concentrations of copper from yearlings through spawning to 3-mo juveniles was found sufficient to establish a "no effect" concentration. No adverse effects were found on survival, growth, or reproductive capacity of trout exposed in a second generation from egg through spawning to copper concentrations (about 9.4, 6.1, and 4.5 μg/liter) which had caused no adverse effects on their parents when exposed to similar concentrations from yearlings to spawning. Nor were any adverse effects found on survival or growth of their offspring when exposed to the same concentrations from hatching to age 90 days. Tissue residue analyses indicated no copper accumulation in gill, liver, kidney, or muscle of either first- or second-generation trout exposed to the various copper concentrations, and residues in unfertilized eggs from exposed females were similar to those in females not exposed to added copper.

ISSN:0706-652X    

DOI:10.1139/f74-073

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Indistinguishable prodissoconch and adult shells, ease of hybridization, and normal meiosis and mitosis in the hybrids support the contention that the Portuguese oysterCrassostrea angulataand the Japanese oysterC.gigasare the same species. By rules of priority the Portuguese is a subspecies of the Japanese oyster. Two hypotheses are given to explain the widely disjunct distribution, by both species arising from a common ancestor or by undocumented introduction. Both oysters are of considerable commercial importance and crossing the two should result in progeny that can be selected for superior commercial traits.

ISSN:0706-652X    

DOI:10.1139/f74-074

出版商:NRC Research Press    

年代:1974

数据来源: NRC