摘要:

Annual surveys of commercial herring oils produced in summer and fall off southwestern Nova Scotia and in winter and spring off southwestern Newfoundland showed iodine values (IV) mostly within the range 135 to 105 in both locations for the years 1965–70. Two systematic trends in IV with season were detected. The first extended uniformly over the whole of each fishery season and was limited to no more than ± 5 IV units. It is believed to represent the influence of long-term average environmental conditions that may vary from year to year and that establish the basic fatty acid compositions of the fish entering the fishery. The second was observed as a seasonal decline, over 2–3 months, of 20 IV units in the Nova Scotia fishery, and of 10 IV units in the Newfoundland fishery. It is proposed that this short-term effect follows from an increase in the relative proportion of the low-density, long-chain, monoethylenic fatty acids characteristic of clupeid oils that could decrease residual fat density at a time of general fat depletion and corresponding density increase for the fish as a whole.Free fatty acids (FFA) in freshly produced oils were also examined. In both fisheries % FFA seldom exceeded 1 and under optimum conditions the % FFA were consistently about 0.2–0.3. Annual seasonal % FFA effects were apparently restricted to an increase in April in the Newfoundland fishery associated with high IV oils of a pink colour denoting heavy spring feeding.

ISSN:0706-652X    

DOI:10.1139/f70-189

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

In cod fillets undergoing deterioration during frozen storage, the dimethylamine content increases (and not the trimethylamine content as previously reported by us). There was no evidence to show an accumulation of dimethylamine in the muscle of frozen scallops, lobster, or shrimp that were purposely held at relatively high storage temperatures. It is suggested that for fish of the family Gadidae dimethylamine might be used as a measure of "frozen-storage deterioration" in much the same way as trimethylamine has been used as a measure of microbial spoilage in the unfrozen fish.

ISSN:0706-652X    

DOI:10.1139/f70-190

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

None of several samplers compared in limited tests in Lake Ontario gave realistic estimates of benthos in all substrates encountered. The Ponar and Shipek grabs, the only samplers that functioned in gravel, came closest to all-sediment samplers. In sand, however, the Franklin–Anderson grab appeared to be much more efficient than either of these two samplers. In mud the Ekman grabs gave the highest mean numbers of animals per m2.In trials in Lake Winnipeg profundal mud, hand-taken diver's core samples being used as a quantitative standard, only the Fisheries Research Board multiple corer and the standard Ekman grab gave quantitative results for total macrobenthos. However, the multiple corer collected significantly fewer chironomids, and the standard Ekman grab significantly fewer oligochaetes, than did the diver's cores. There were indications that the tall Ekman grab was either not tall enough or too heavily weighted for use in soft sediments and that a small improvement in design could make both this and the standard Ekman more efficient. Most of the samplers apparently sampled some groups of organisms much better than others. Neither the Ponar grab nor the tall weighted Ekman grab sampled the chironomid or oligochaete populations satisfactorily. However, both grabs indicated densities of sphaeriids not significantly different from the diver's samples.

ISSN:0706-652X    

DOI:10.1139/f70-191

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A near-resonant mode of oscillation extending to the continental shelf in the Gulf of Maine is shown to be a contributing factor in the extreme high M2tidal ranges in the Bay of Fundy.The effect on the M2tidal regime of a double barrier at Cape Chignecto is studied by two methods. A one-dimensional simple harmonic model shows the effect of placing the matching boundary at any intermediate position and defines a probable zone of values for the barrier amplitude. A two-dimensional calculation covering the entire resonant region gives an estimated amplitude reduction of 34% at the Cape Chignecto barrier site.

ISSN:0706-652X    

DOI:10.1139/f70-192

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Preferred temperatures were determined for yearling lake trout acclimated to 5, 10, 15, and 20 C. Acclimation temperature had virtually no effect on preferred temperature. The final preferendum was 11.7 C, which is about 2 degrees C warmer than the temperature at which lake trout are most commonly caught in thermally stratified lakes.

ISSN:0706-652X    

DOI:10.1139/f70-193

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The external metamorphosis of the sea lamprey was divided into four stages, based primarily on the condition of the mouth: mouth reduced, mouth fused, mouth enclosed, and mouth elongated. During metamorphosis, the eye enlarged greatly, the snout and mouth region changed from a fleshy hood enclosing a sieve apparatus to a large sucking disc, the nasopore membrane and the branchial area shrank, the branchiopores changed in shape, the general color changed from dark brown and yellow to an intense blue-black dorsally and white ventrally, and the total length increased. Metamorphosis began in early to mid-July and did not take place after August. The duration of external metamorphosis was about 3 months for lampreys transforming under natural conditions. The mean lengths of metamorphosing lampreys from tributaries of lakes Superior and Michigan were 145 and 136 mm, respectively.

ISSN:0706-652X    

DOI:10.1139/f70-194

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Results of gear evaluation experiments to determine the feasibility of capturing sablefish in king crab-type pots indicated that catch rates decreased significantly as the fishing time increased. Pots were most effective when equipped with triggered tunnels and without attraction lights. Although subsequent commercial feasibility trials were hampered by bad weather, a catch of 18,754 lb of marketable sablefish in 112 pot hauls for an overall average of 4.7 lb a pot per hour illustrated the potential value of pot fishing.

ISSN:0706-652X    

DOI:10.1139/f70-195

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A review of the morphometric and meristic variations in 893 specimens of the burbot (Lota lota) from 18 freshwater areas representing the range of the species, showed thatLota lota lacustris(=maculosa), with a short, high caudal peduncle and low meristic values may be distinguished fromLota lota lota, with a long, low caudal peduncle and high meristic values.Lota l.lotaoccurs from the Volga River system through Siberia and Alaska to the Mackenzie River system in Canada. The populations from the Elbe River and the Danube River are on the periphery of this subspecies, to which it clearly belongs.Lota l.lacustrisoccurs in southernmost Canada, the United States, and western Europe. BothLota l.leptura(Hubbs and Schultz, 1941) andLota l.kamensis(Markun, 1936) are synonyms ofLota l.lota(Linnaeus, 1758).Clinal variations in the means for various characters of the species were found as follows. All meristic values and length of the caudal peduncle as a percentage of standard body length, in general, increased eastward from western Europe as far as 120°E and then decreased toward New England. Predorsal and preanal lengths generally increased eastward from western Europe to New England. The following generally decreased from western Europe eastward to 120°E and then increased toward New England: head length, interorbital width, postpectoral length, and depth of caudal peduncle as a percentage of standard length; depth of caudal peduncle as a percentage of its length; and postpectoral length as a percentage of predorsal length.

ISSN:0706-652X    

DOI:10.1139/f70-196

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

By means of serial slaughter the rate of gastric digestion in yearling sockeye salmon (30–40 g) was studied at approximately 3, 5, 10, 15, 20, and 23 C, after satiation feeding on Abernathy pellets. Subsequently the ash-free dry weight of the stomach contents was determined and expressed as a fraction of the dry weight of the fish. At any one temperature, rate of digestion appeared to be proportional to the mass of food remaining in the stomach (exponential decline). The time for complete digestion decreased from 147 hr at 3 C to 18 hr at 23 C. The time for one-half of a sample of fish to exhibit empty stomachs corresponded closely to that for a mean state of 96% gastric digestion, providing a simple means for determining rate of digestion.

ISSN:0706-652X    

DOI:10.1139/f70-197

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

During 1963–66, a trawl and echo-sounder survey was conducted in the northeast Pacific Ocean to investigate the distribution and abundance of rockfish (Scorpaenidae) species, particularly Pacific ocean perch (Sebastodes alutus), inhabiting the outer continental shelf and upper continental slope from Cape Blanco, Oregon, to Unalaska Island, Alaska. Rockfish predominated in most trawl catches. Among areas, numbers of rockfish species declined northward, from 19–21 in the Oregon–Vancouver Island region to 5 off Unalaska Island. Within areas, maximum numbers of species were caught at intermediate depths — usually 80–139 fath (146–254 m). With rare exceptions, Pacific ocean perch was the predominant rockfish species in the trawl catches throughout the study area, although its relative abundance declined from north to south.Within areas, ocean perch catch rates were usually maximal at intermediate depths — 120–139 fath (220–254 m) in summer and substantially deeper in winter. Juvenile fish usually occupied shallower depths than adults, but were often in the company of large adults. Among areas, summer catch rates were relatively high off southwest Vancouver Island and southeastern Alaska and in the western Gulf of Alaska. Off Vancouver Island, summer catch rates were higher than winter catch rates, particularly for large adults of both sexes. Echo-sounder records indicated schools were frequently unavailable to the on-bottom trawl used in this survey.Ocean perch in the northeast Pacific Ocean were categorized, tentatively, into B.C.- and Gulf-types, whose mutual boundary is Dixon Entrance. Separation was based on differential size distributions and year-class strengths.Survival rates among year-classes were evidently quite variable, particularly for the Gulf stock west of Cape Spencer.Qualitatively, ocean perch abundance generally increased from south to north in the study area.Bottom-water temperatures varied inversely with depth and latitude. Among areas, temperature range at depths of maximal ocean perch catch rate was 4.5–7.7 C, but in high-abundance areas the temperatures did not exceed 6.0 C. Seasonally, temperature at depths of maximal catch rate varied approximately 1.5 C.

ISSN:0706-652X    

DOI:10.1139/f70-198

出版商:NRC Research Press    

年代:1970

数据来源: NRC