摘要:

During the past century the Eurasian and North African range of the brown trout,Salmo truttaL., has been extended to include discontinuous populations on all continents except Antarctica. Primary factors affecting the establishment of naturalized populations are water temperature, precipitation, and suitable spawning grounds. Any future major expansion in the world distribution of the brown trout, with the possible exception of Asia, is unlikely.

ISSN:0706-652X    

DOI:10.1139/f68-225

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

From the literature there was a doubt as to whether interrenalectomy would result in elevated plasma potassium levels in a elasmobranch; in this study, no elevation was observed by comparison with sham-operated thorny skate (Raja radiata) held in sea water for up to 44 days post-operative.Blood calcium levels were significantly elevated in the interrenalectomized animals between 13 and 23 days but the increase was only 10%.There was no change in osmolality, sodium chloride, magnesium, or urea which can be attributed to interrenalectomy. Noteworthy was the manner in which both sham and interrenalectomized animals were able to maintain plasma electrolyte levels during the long period of starvation after surgery. Whenever significant changes occurred during the course of the experiment, sham and interrenalectomized fish were similarly affected, apart from the exception noted for calcium.Plasma urea levels were significantly depressed after interrenalectomy when the skates were held in a 3:1 mixture of sea water: fresh water for 7–9 days. The same trend was observed for sham-operated animals but the decrease was not significant. Normal animals maintained plasma urea in 75% sea water but not in 60% sea water.

ISSN:0706-652X    

DOI:10.1139/f68-226

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The stomachs of 17 cetaceans of seven species (3Kogia simus, 5Stenella longirostris, 3S.graffmani, 2Lagenorhynchus obliquidens, 2Delphinus delphis, 1Lissodelphis borealis, and 1Phocoena sinus) yielded 18,164 fish otoliths representing over 51 species, 40 genera, and 22 families. Lanternfish (family Myctophidae) otoliths accounted for more than 89% of the total, and they had come from at least 19 species belonging to nine genera. Only two fish species could have been identified if we had not been able to utilize otoliths. To be useful in food studies involving otoliths, cetacean stomachs cannot be placed in formalin solutions, even for short periods.The kinds and diversity of species preyed upon by several of these cetaceans indicate that they routinely forage in depths of 650–800 ft (200–250 m), and a few such asKogia simusmay descend to 1000 ft (300 m) or deeper.

ISSN:0706-652X    

DOI:10.1139/f68-227

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Fifty-eight Arctic Alaskan lakes and rivers and two ponds as well as a few northwestern Arctic Canadian waters were analyzed for two or more physical or chemical characteristics. The waters sampled were nearly all of the bicarbonate type and ranged from very soft to hard. The Alaskan and mainland Canadian lakes contain levels of many ions similar to those of some low electrolyte lake waters previously reported for the north temperate zone. The characteristics measured, with the mean values for the Alaskan waters in brackets when 20 or more lakes or rivers were sampled, were: calcium (17.2 mg/liter), magnesium (2.1 mg/liter) total iron, total alkalinity (50.3 mg/liter), sulfate (4.9 mg/liter), chloride (3.8 mg/liter), nitrate, phosphate, electrical conductance (116 μmho),pH (7.7), and water color (24 Pt units). One of the ponds, analyzed for 18 trace metals, indicated relatively high concentrations of iron manganese, zinc, and copper. Correlation coefficients (ratP < 0.5) between various characteristics were: electrical conductance and total alkalinity, 0.98; electrical conductance and calcium, 0.97; electrical conductance and magnesium, 0.42; calcium and magnesium, 0.46; andpH and total alkalinity, 0.91. On the Coastal Plain of Arctic Alaska the total electrolyte content of lakes lying within 25–50 km from the Arctic Ocean was noticeably raised by chloride additions.

ISSN:0706-652X    

DOI:10.1139/f68-228

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

For white sturgeon taken incidentally in the salmon gillnet fishery in the Fraser River during the summer of 1962, pectoral fin ray sections indicated that over three-quarters were fish aged 9–16 years. Gillnets for salmon apparently select sturgeon over a size range between 30 and 60 inches. Back-calculation of size attained at previous ages indicated that after attaining a length close to 20 inches by age 5, the sturgeon grow about 2 inches per year to about age 25. Limited data from pectoral fin ray sections suggest that age at first spawning is from 11 to 22 years for males, and from 11 to 34 for females. Subsequent spawning is apparently at intervals of 4–9 years. Fraser River sturgeon are more piscivorous than has been recorded for white sturgeon and other sturgeon species elsewhere, about one-half of the stomachs containing fish, especially eulachons. The age distribution in the catch, though biased by selection, was used to estimate rates of natural and fishing mortality. The eumetric fishing curve suggests that present yield could be increased by a greater size at first capture, particularly if the natural mortality rate is as low as 0.05. The history of the sturgeon fishery suggest that sustainable yield could exceed 100,000 lb per year. The commercial landings in recent years average 30,000–40,000 lb. The sport fishery may take an additional 20,000–30,000 lb. Sustained yield in the circumstances of the present fishery could be 80,000 lb per year, about 25% more than the present catch. Some recommendations are made for management, stressing the importance of protection of an annual spawning population of 300–600 females.

ISSN:0706-652X    

DOI:10.1139/f68-229

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The respiratory metabolism of groups of goldeye was measured during rest and sustained swimming activity at 5, 10, and 15 C under conditions of continuous reduction in oxygen by the metabolism of the fish. The oxygen consumption fell progressively during swimming at all temperatures indicating dependence of metabolism on oxygen supply at allpO2levels. During rest the oxygen consumption was relatively independent ofpO2until certain critical levels were reached. Respiration became markedly limited by CO2in the medium when thepCO2exceeded 50 mm Hg. It is apparent that survival possibilities of goldeye would be limited bypO2andpCO2between 20–40 mm Hg during the winter.

ISSN:0706-652X    

DOI:10.1139/f68-230

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

In the summers of 1966 and 1967, very low surface temperatures, about 11 C, and weakly stratified water occurred along the western coast of the Gulf of Maine at Cape Nedick, in the Sheepscot River, and off Vinalhaven Island at the mouth of Penobscot Bay. Moderately low temperatures, about 13 C, were found often between the islands of Casco Bay. These low temperatures indicate an active vertical mixing, associated with tidal currents, that transports water warmed at the surface downward and cold water upward.Where tidal mixing is reduced, offshore from Cape Ann and in the landward confines of Casco Bay, surface temperatures over 17 C and pronounced stratification occurred. When these high temperatures were observed off Cape Ann, the weather was sunny and calm, or a light wind caused very little mixing. Within Casco Bay temperatures of 17 C or more were observed during a period when fogs were prevalent, allowing heating in clear spells in the daytime and a minimum of cooling at night.

ISSN:0706-652X    

DOI:10.1139/f68-231

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Cryogenic preservation of cod sperm, with retention of fertilizing capacity, was achieved. Sperm were deep frozen to −79 C or −196 C in the presence of protecting agents. Of the conditions tested, most satisfactory freezing was accomplished in a mixture containing 1 part semen and 3 parts of a medium that consisted of 40 parts 0.4 MNaCl − 0.1 Mglycine: 8 parts of 1.3% sodium bicarbonate: 10 parts of glycerol. A freezing rate of 5 degrees C/min was more successful than one of 1 degree C/min.When frozen sperm were stored at −196 C for periods up to 60 days the average fertility was 36 ± 12% (seven samples) compared with 79 ± 6% (seven samples) for fresh sperm on the same batch of eggs. Successful storage of cod sperm at −79 C for a year was achieved.

ISSN:0706-652X    

DOI:10.1139/f68-232

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Transplants of specimens ofBalanus balanoidesfrom North Wales to Newfoundland, Canada, confirmed two innate differences between European and North American forms of the species. Breeding took place later in transplanted European populations. The eggs of the European form, though maturing later and therefore at a slightly lower temperature than the North American form, were distinctly smaller.The time of breeding both in the North American and European forms was earlier at higher latitudes, at higher shore levels, and in shelter.

ISSN:0706-652X    

DOI:10.1139/f68-233

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Preliminary sampling revealed the presence of furunculosis disease in the resident brook trout population of the southern Ontario trout stream used in this study.Two plantings of marked yearling brook trout were made in the study area in 1966; one in the spring, and the other in the fall. The spring planting consisted of 1000 brook trout with a predetermined incidence of furunculosis infection and an equal number of trout with no evidence of infection. The fall planting consisted of 2000 brook trout with a known incidence of furunculosis infection.The stream was electrofished periodically during the 2-year period after the first planting. A total of 445 brook trout (140 of the planted hatchery stock, and 305 resident trout) and 127 fish of associated species were captured and examined for the presence ofAeromonas salmonicida, causative agent of furunculosis.Recovery rates of the "infected" and "noninfected" stocks of brook trout were similar, and there was no evidence of transmission ofA.salmonicidafrom the infected fish to the control fish, nor the resident population of brook trout and other species of fish captured.

ISSN:0706-652X    

DOI:10.1139/f68-234

出版商:NRC Research Press    

年代:1968

数据来源: NRC