摘要:

We conducted laboratory respirometry trials using adult sockeye salmonOncorhynchus nerkaimplanted with electromyogram (EMG) radio transmitters to investigate the relationship between oxygen consumption and EMG pulse interval. The strong association that was observed suggested that EMG telemetry could be used to assess activity and, thus, relative energy expenditure in freely migrating sockeye salmon. Using EMG telemetry, we then assessed the relative energy costs of upstream migration by adult sockeye salmon through specific reaches of the Fraser River, British Columbia. Greatest energy costs were incurred during migration through Hell's Gate fishways, a known point of difficult passage. Another energetically demanding area was a gravel bar that had not been previously identified as difficult for passage. Three other areas that historically had been identified as difficult for passage were energetically less expensive to migrate through during our study. Our results demonstrate that EMG telemetry identified features and reaches of the river that impeded upstream migration, and they provide insights into the behavioural responses of fish to areas of difficult passage.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0253:UOETTA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We estimated long-term tag-shedding rates for lake troutSalvelinus namaycushusing two existing models and a model we developed to account for the observed permanence of some tags. Because tag design changed over the course of the study, we examined tag-shedding rates for three types of numbered anchor tags (Floy tags FD-67, FD-67C, and FD-68BC) and an unprinted anchor tag (FD-67F). Lake trout from the Gull Island Shoal region, Lake Superior, were double-tagged, and subsequent recaptures were monitored in annual surveys conducted from 1974 to 1992. We modeled tag-shedding rates, using time at liberty and probabilities of tag shedding estimated from fish released in 1974 and 1978–1983 and later recaptured. Long-term shedding of numbered anchor tags in lake trout was best described by a nonlinear model with two parameters: an instantaneous tag-shedding rate and a constant representing the proportion of tags that were never shed. Although our estimates of annual shedding rates varied with tag type (0.300 for FD-67, 0.441 for FD-67C, and 0.656 for FD-68BC), differences were not significant. About 36% of tags remained permanently affixed to the fish. Of the numbered tags that were shed (about 64%), two mechanisms contributed to tag loss: disintegration and dislodgment. Tags from about 11% of recaptured fish had disintegrated, but most tags were dislodged. Unprinted tags were shed at a significant but low rate immediately after release, but the long-term, annual shedding rate of these tags was only 0.013. Compared with unprinted tags, numbered tags dislodged at higher annual rates; we hypothesized that this was due to the greater frictional drag associated with the larger cross-sectional area of numbered tags.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0261:COTNMT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Previous field studies suggest that the preference for an optimal temperature is often overridden by a stronger preference for other habitat variables such as physical structure. I used a temperature gradient tank with various treatments of ration, prey availability, and cover to test the relative importance of these factors in conjunction with temperature on habitat selection by individual smallmouth bassMicropterus dolomieu. The presence of food and cover (presented in separate experiments) significantly affected the temperature selected by smallmouth bass. Fish presented with a limited amount of food at a position of greater than preferred temperature in the tank increased the time spent at high temperatures, whereas fish allowed to feed till satiated retreated to the cold end of the tank for most of the day. When cover was present at the warm end of the tank, the mean time spent in this area was five times greater than when no cover was present in the tank. The preference for cover at high temperatures contradicts expectations based solely on bioenergetic considerations. However, the reduced activity of fish using cover at higher temperatures suggests that the increased metabolic costs incurred during exposure to high temperature can be offset by decreased activity costs. These results suggest that even when temperature is not a primary consideration in habitat selection, its effects are often mediated through other behavioral responses.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0274:RIOTFA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We recorded habitat variables including macrohabitat type (run or pool), substrate, cover type, stream depth, and light level periods for focal point observations of smallmouth bassMicropterus dolomieuwhile snorkeling along transects in the Buffalo River, Arkansas. We used logistic regression analysis to determine which habitat variables were important in discriminating between the presence of age-0 (<100 mm) and older fish as an indication of microhabitat segregation. Runs and pools were occupied by both groups of smallmouth bass, though a higher proportion of age-0 fish were observed in pools. Age-0 smallmouth bass were not restricted to stream edges and runs as in some eastern United States streams. A fitted model for run microhabitats indicated that bedrock, silt, sand, gravel, aquatic macrophytes, boulders, and light period were significant predictors of an age-0 smallmouth bass observation. Significant predictors in pool microhabitats included cobble, undercut banks, depth, and light. Thus, we found evidence of intraspecific microhabitat segregation in the Buffalo River. We conclude that Buffalo River smallmouth bass are habitat generalists and may not be a good indicator species of the effects of habitat alterations. Our evidence of intraspecific habitat segregation indicates the need to identify relations between habitat use and survival of age-0 fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0284:IHSBSB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Current and historical age structure information on the Yellowstone–Sakakawea stock of paddlefishPolyodon spathulais reviewed in relation to the completion of Garrison Dam in 1953 and the subsequent filling of Lake Sakakawea, a 156,000-ha impoundment on the Missouri River. Paddlefish abundance increased greatly after the closure of Garrison Dam, and the first large group of paddlefish (nearly all males) migrated up the Yellowstone River to Intake, Montana, in 1962–1963. By the mid-1970s, after the gradual filling of the reservoir (1954–1966), both females and males had fully recruited to the Intake fishery, and more females were harvested than males. By the 1980s, older females predominated in the harvest. Based on age determination in 1991–1993, the stock has continued to age, from a mean of 10.3 years in 1964–1965 to 14.8 in 1974, 20.3 in 1985, and 23.5 in 1992. In 1993, however, mean ages of paddlefish at Intake decreased by 2 years for males and 3.3 years for females. In 1991 and 1992, males from Intake were characterized by bimodal age distributions with ages ranging from 7 to 40 (means, 18.4 and 17.8, respectively); females demonstrated unimodal age distributions and ranged in age from 10 to 42 (means, 25.5 and 26.1). Males commonly matured at age 9. but females almost never matured before age 15. The oldest paddlefish encountered was a 14-kg male caught in 1985 and estimated to be 55 years old. Although substantial recruitment has occurred within the past decade (as indicated by recruitment of 9–11-year-old males to the fishery in 1991–1993) and reproduction appears to have occurred in 1991 and 1993 (based upon counts of young-of-the-year in Lake Sakakawea), the age structure suggests that recruitment may be less in recent years than in the years soon after the reservoir was closed and filled. A conservative harvest is called for until it is clear that reproduction is adequate to sustain the stock and the fishery.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0291:ASOTYS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Despite the importance of the recreational fishery for striped bassMorone saxatilisalong the eastern coast of the United States, little is known about the survival rates of caught and released striped bass. We predicted long-term (58-d) hooking mortality of striped bass after catch and release in saltwater using a logistic regression model. Experimental fishing was conducted on fish (27–57 cm) in a 2-ha saltwater impoundment in Salem, Massachusetts. Depth of hook penetration in the oral cavity, anatomical site of hooking, gear type (treble or single hooks), and angler experience were significantly related to mortality (P< 0.05). The logistic regression model was developed with backwards stepwise selection to predict probability of death from hooking. The final model included depth of hook penetration, gear type, and angler experience as predictor variables. Predicted mortality ranged from 3% under the most favorable conditions to 26% for the worst set of conditions. Predicted as well as observed mortality for the entire experimental group was 9% which is generally much lower than reported in striped bass hooking mortality studies conducted in freshwater. At the end of the experiment, condition factors were significantly lower for surviving hooked fish than for fish that had not been hooked.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0300:MOSBHA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Freshwater-acclimated subadult striped bassMorone saxatilisthat had undergone cannulation of the dorsal aorta were exercised against a water current at 100 cm·sec−1(2–3 fork lengths·sec−1) for 5 min in freshwater and placed in flow-through holding boxes in a recovery tank at 25°C. Recovery tanks contained water with either 0 (freshwater, FW), 10 (brackish water, BW), or 30 (seawater, SW) g NaCl·L−1or 10 mM NaHCO3−·L−1(buffered freshwater, BFW). A postexercise metabolic acidosis (decreased postexercise blood pH and increased blood lactate) was compensated within 2–4 h in all recovery environments except SW. Arterial O2tension and cortisol, glucose, and hemoglobin concentrations transiently increased immediately after exercise, and arterial CO2tension and HCO3−generally decreased. Plasma Cl−did not change until 2–4 h postexercise, when decreases (FW and BFW), an increase (SW), or no change (BW) indicated passive fluid or Cl−exchanges with the recovery environment. Increasing plasma Cl−in the SW recovery environment inhibited HCO3−retention or uptake, which slowed pH compensation. In summary, postexercise acidoses were corrected and ionic imbalances were minimized by recovery in brackish water (10 g NaCl·L−1).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0308:SBEAHS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The effect of playing time on physiological responses and mortality of striped bassMorone saxatilis(<36.0 cm total length) captured by hook and line was evaluated in summer (26–32°C water temperature) and fall (16–19°C water temperature). Elevated plasma cortisol concentrations were observed in fish angled in summer only, and the response occurred only in fish played more than 2.5 min. Hyperglycemia was evident in fish angled in summer only and was proportional to playing time. Plasma osmolality and lactate concentrations increased with playing time during both seasons and were proportional to playing time. Mortality of fish recovered 31–42 d after hooking was 11.7% in summer and 5.7% in fall, and it was not related to playing time in either season.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0321:NPRAMO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We tested the effects of transport containers and transport water treatments on the survival of field-collected delta smeltHypomesus transpacificus, a threatened osmerid endemic to the Sacramento–San Joaquin estuary in California. Use of cylindrical polyethylene bags instead of rectangular coolers as transport containers increased survival from 40.7 to 83.6% at 4 h postcollection, from 11.9 to 33.1 % at 48 h, and from 6.9 to 27.9% at 72 h. Addition of NovAqua, a commercial water conditioner containing polymers, to transport water of 8‰ NaCl significantly increased 72-h survival (54.8%) over that of the 8‰ NaCl control (27.9%). Survival of fish lightly anesthetized with MS-222 (tricaine methanesulfonate) during transport was intermediate between the NaCl and NaCl plus NovAqua treatments. Survival of delta smelt in the NaCl plus NovAqua treatment also improved from August through November, as fish increased in size and water temperature decreased. Improved survival of delta smelt treated with NovAqua was probably related to the polymers, which may have reduced physiological stress responses, such as osmotic imbalance.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0326:UOSAAP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The assumption that marking does not alter the vulnerability of fish to a visual predator was examined. Similar numbers of age-0 steelheadOncorhynchus mykisswere tagged with binary-coded-wires, tagged with passive integrated transponders, freeze branded, marked with fingerling tags, or left unmarked. All were subjected to age-1 steelhead predators for 24 h in 2.4-m-diameter circular tanks filled with clear well water. Twice as many marked as unmarked age-0 steelhead prey were eaten. There was no significant survival difference among the four marked treatment groups, which suggested that in the laboratory the trauma associated with marking is more important than mark type. We conclude that marking may effect postrelease survival and recommend that mark–recapture experiments be used to empirically determine and correct for differences in survival of marked and unmarked fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0330:VOMAST>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor