摘要:

A high volume pump (2.5 m3/min capacity at 6 m head) and conventional plankton nets (0.5 and 1.0 m diam) were operated side by side in two tests to evaluate the efficiency of each gear for sampling fish larvae within the intake structure of a coastal power plant. At intake channel current velocities up to 40 cm/s (the maximum tested), the pump in one test caught significantly more fish larvae than the nets. Compared to the pump, both sizes of plankton nets in each test greatly undersampled large larvae (over 5.0 mm total length). Our findings suggest that conclusions regarding ichthyoplankton entrainment based on data obtained with conventional plankton nets may be of questionable validity.Key words: ichthyoplankton, entrainment, pump, nets

ISSN:0706-652X    

DOI:10.1139/f79-011

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Dorsal aorta blood samples were taken from cannulated rainbow trout (Salmo gairdneri) exposed to pH 4.0 (acid group) or pH 7.0 (controls) in normocapnic conditions at 10 °C. Over a 5-d period there was a significant gradual decrease in pH and total CO2in the acid group but no significant difference inpO2and lactate compared to the controls. After uncannulated rainbow trout were exposed to the same conditions for 12 d there were significant increases in hemoglobin, hematocrit, and erythrocyte levels in caudal vein samples from the acid group. The results show that rainbow trout exposed to acid without hypercapnia develop acidaemia which is not a result of anaerobic respiration. The increase in erythrocyte concentration probably offsets the effects of acidaemia upon blood oxygen carrying capacity. Differences in ambientpCO2and/or species differences could account for varying acid-base values in acid exposed fish reported by different workers.Key words: environmental acidification, acidaemia, lactate, pH, total carbonate, fish

ISSN:0706-652X    

DOI:10.1139/f79-012

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Eleven dye substances were tested for their ability to stainMyxosoma cerebralisand to be retained through either the pepsin-trypsin-dextrose or the plankton centrifuge method of releasing and concentrating spores. Silver nitrate proved to be the best; it produced a distinctive brown color that has been retained by spores through 2.5 yr of storage. The method has applications in histologic studies of whirling disease, in quantifying the efficiency of spore detection procedures, and in teaching.Key words: myxosporidans,Myxosoma cerebralis, whirling disease, spore staining

ISSN:0706-652X    

DOI:10.1139/f79-013

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The incidence of precocious steelhead trout (Salmo gairdneri) was determined in several Idaho hatchery steelhead populations. The range of incidence of precocious males was 0–64% of the sampled populations. This variation appeared to be related to age of the trout, water temperature, and photoperiod. The incidence of precocious males greatly exceeded the incidence (0.1% of the population when encountered) of precocious females. Precocious male steelhead trout are apparently lost from the migrating smolt population and display mating behavior similar to sea-run adult male steelhead. Precocious males maintained in laboratory conditions remained sexually mature for at least 6 mo of observation. This was reflected by mean gonadal weights and mean gonadosomatic indices from precocious male steelhead which differed significantly from nonprecocious juvenile male steelhead maintained under similar conditions. No consistent pattern of growth was observed among laboratory-maintained trout.Key words: steelhead trout, reproduction, precocious sexual maturation, age, photoperiod, temperature

ISSN:0706-652X    

DOI:10.1139/f79-014

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The effect of size at the time of ablation on postoperative survival was assessed by removing the eyestalk from 4th, 5th, and 6th stage juvenile American lobsters (Homarus americanus) 6 d postmolt. The 6th stage juveniles exhibited significantly higher survival (72.8%) through three postoperative molts than the 5th or 4th stage lobsters (45 and 30% survival, respectively). Survival of control lobsters through the same number of molts was 90%. The feeding of a nutritionally adequate diet (frozen brine shrimp) was of prime importance with regard to survival of both ablated and control lobsters. The mean percent total weight gains for these three postablation molts were 610, 571, and 642% for 4th, 5th, and 6th stage lobsters, respectively, while the weight gain for control lobsters was 407%. The data suggest that eyestalk ablation should not be performed earlier than 6th stage for maximum survival and growth.Key words: eyestalk ablation, American lobster, survival, growth

ISSN:0706-652X    

DOI:10.1139/f79-015

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The standard religion of Pacific salmon research and management was developed by the 1930s and persists today: that adequate husbandry of the resource requires research on the biology of salmon, regulation to ensure sustained yield, protection of the environment to ensure the means of production, and enhancement measures to augment natural production and to mitigate effects of imperfect regulation and protection. Through the 1930s into the 1950s, there were substantial gains in understanding the biology of salmon and relating it to management. Salmon cultural techniques fell into disrepute. In the 1950s and 1960s, the pressures of other resource uses and international conventions greatly expanded perceptions of management and stimulated major discoveries about salmon biology. Economists began to seriously examine the salmon fisheries and perceived the need for limited entry. By the late 1960s the salmon fishery had become highly complex and there was a resurrection of the erstwhile hopes for salmon culture as an integral part of management. Planning exercises for the Salmonid Enhancement Program underlined that integration into a total system of management was crucial to success.For the future, for salmon to be doubled in abundance rather than halved, the manager's perspective must be more closely identified with that of salmon. In addition to the continuing needs for protection of environment and a broadly balanced enhancement program with an appropriate amount of research and evaluation, there are some necessary changes in attitude concerning regulation. Undernocircumstances should the permissible harvest of any race of salmon be exceeded. Day-to-day regulation should be geared to salmon biology, not human convenience. Experimental regimes of regulation should be undertaken with suitable commitment to long-term research. Unless such measures are taken, it is realistic to speculate that "maybe we can't get there from here."Key words: Pacific salmon, resource management, salmonid enhancement

ISSN:0706-652X    

DOI:10.1139/f79-016

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f79-017

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f79-018

出版商:NRC Research Press    

年代:1979

数据来源: NRC