摘要:

As a test of the match–mismatch hypothesis, we examined the effects of prey availability and water temperature on growth and survival of weekly cohorts of larval threadfin shadDorosoma petenensein J. Strom Thurmond Reservoir, Georgia–South Carolina. Hatching dates were estimated from otolith increments, and availability of prey was estimated from the abundance of zooplankton size-classes commonly eaten by larval threadfin shad. Growth rates of 31 cohorts ranged from 0.39 to 0.78 mm/d, demonstrating the potential for stage-duration effects on cohort survival. Daily growth rate was related to water temperature and prey availability for larvae up to 21 d old. Growth increased linearly with water temperature up to 28°C, but the relation between growth and prey availability was more complex. Growth rate increased with prey density up to 160–290 organisms/L; at higher densities, growth rate decreased or was unchanged. Cohort survival ranged from 0.65 to 0.96 (per millimeter increase in length) and was significantly correlated with water temperature and growth rate but not with prey availability.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0999:EOTAZA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Enclosure traps that quickly surround well-defined areas of habitat are perhaps the most widely used method for sampling fishes in vegetated habitats. However, relatively few data are available to evaluate the effects of habitat structure on sampling characteristics of enclosure traps. In this study, we determined how clearing efficiency and accuracy of 1-m2throw traps varied across a range of environmental conditions in the Florida Everglades by sampling within enclosed areas of marsh habitat. Throw trap clearing efficiency and sampling accuracy did not differ among two widely separated locations and appeared to be unaffected by variation in water depth, canopy height, plant cover, plant stem density, and periphyton volume. Sampling accuracy averaged 63% of fishes present after correcting for clearing efficiencies. On average, 83% of the fishes present in a throw trap were recovered. Therefore, it appeared that about 17% of the missing fishes may have burrowed into the substrate or been discarded with sorted detritus. In contrast, the remaining 20% of fishes probably avoided the throw trap. This is the first study to differentiate between potential sources of throw trap sampling errors. Importantly, density estimates obtained by throw traps were positively correlated (r= 0.82) with actual population densities. Mean fish lengths and fish size distributions obtained by throw trapping usually did not differ from actual mean lengths or fish size distributions. Finally, high concordance of fish species ranks indicated that throw traps accurately described fish community structure. Throw traps appeared to provide relatively accurate estimates of fish density, fish size, and community structure across a range of environmental conditions.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<1012:SFIVHE>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The diversity of statoliths and changes in statolith length were examined in larval and metamorphosing sea lampreysPetromyzon marinasfrom four streams in Ontario. In midsummer, increases in statolith lengths were similarly and positively correlated with larval total lengths in the four streams. Statoliths from larval and metamorphosing lampreys collected from Lynde and Farewell creeks in June and September displayed typical alternating opaque and translucent bands. The number of opaque bands, or annuli, provided reliable age estimates when compared with length-frequency distributions. In July and September, statoliths from some larval and metamorphosing lampreys collected from West Root River and Cannon Creek were either absent or did not have typical bands, hence they did not always provide reliable ages. The diversity of statoliths appears to be related to ambient calcium ion concentrations, especially during periods of rapid larval growth. The use of statoliths is sometimes the only method to age some populations of sea lampreys because of ambiguity in length-frequency distributions. The absence of statoliths, as encountered in this study, has potential management implications when determining age-at-metamorphosis.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<1021:NADASD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Eight-day-old striped bassMorone saxatilis(6.17–6.22 mm, total length) were fed twice daily at three feeding rates to produce three growth rates. Fish were sampled once per week for 4 weeks to determine total length and otolith radius. Feed ration treatments resulted in discrete size-classes of striped bass after 4 weeks with a 27% difference in mean length between the low and high feed ration treatments. No significant differences in slope or intercept for the regression of fish length on otolith radius were observed among treatments, suggesting that slow growth alone may not be sufficient to result in decoupling of the otolith size–fish size relationship in striped bass.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<1027:SGDNDT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We evaluated a bioenergetics model for adult largemouth bassMicropterus salmoidesat two temperatures (22°C and 27°C) and two feeding levels (ad libitum and 2% wet body mass) in the laboratory. Three statistical methods were used to assess agreement between predicted and observed growth and consumption during a 9-week period. Multivariate profile analysis indicated no significant deviations between predicted and observed mean body masses at the end of each week of the experiment; partitioning mean square error revealed that 87% of the variance was attributed to random variation rather than to systematic variation; and a reliablility index indicated agreement between predicted and observed masses within a factor of 1.03. Predicted cumulative food consumption during the 9-week period was 9.4% less than that observed. Model predictions of mean daily consumption rates closely tracked observed values when fish were not fed to excess, but the model did not perform as well under ad libitum feeding conditions. However, multivariate profile analysis detected no significant deviations between predicted and observed mean consumption rates from each week; random variation was the largest source of error (78%); and the reliability index showed agreement between predicted and observed mean weekly consumption rates within a factor of 1.38. Agreement between model estimates and observed growth and food consumption further corroborates the largemouth bass bioenergetics model within the limited range of temperatures and feeding conditions tested.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<1030:LEOABM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Passive integrated transponder (PIT) tags potentially allow the automated recording of the movements of individual animals. Here we describe a system designed to log the activity patterns of fish that use a discrete refuge when they are not feeding. The system was demonstrated with juvenile salmonids, which in winter seek shelter during the day in crevices under stones in the streambed but emerge to feed at night. The PIT tag antennae monitored a tube connecting a refuge to a standard hatchery tank and recorded each movement of a fish in or out of the refuge. This method allowed the quantification of individual time budgets for a group of fish sharing the same tank. The efficiency of the system was high, but occasionally the direction of movement could only be ascertained by referring to the previous position of the fish. The technique revealed very synchronized movement by Atlantic salmonSalmo salarout of the refuge at dusk and into it at dawn and intermittent brief excursions from the refuge during daylight hours. The system could be adapted for any species that is large enough to be given a PIT tag and that uses a refuge or burrow (e.g., for breeding or predator avoidance).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<1036:AASFMF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We designed and tested a wooden box splitter for use in subsampling estuarine Ichthyofauna in the field. Results showed that the splitter operator had a significant effect on the estimation of the original sample volume whereas the splitter being used did not. Estimates of the original sample volumes of water or original fish abundances were biased. Coefficients of variation ranged from 1.90% to 4.10% for the volumetric subsamples and from 0.00% to 29.02% for fish abundance subsamples. The precision of estimates of abundance or of species composition decreased with increased splitting. However, the species composition and length-frequency distribution of the original samples were preserved in the subsamples for 75% or more of the first-level splits. This subsampling device is practical in the field and statistically adequate for use in a fisheries program.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<1041:EOANTO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.6.1048

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor