摘要:

The relationships between age-specific total lengths, weights, condition factors, and a measure of the thermal opportunity for growth (TOG; calculated as the sum of degree-days greater than 5°C) were estimated for lake sturgeonAcipenser fulvescensfrom data available for 16 populations spread throughout much of the species' natural range. The TOG explained a significant proportion of the observed variation in length at age irrespective of age. Correlations between weight at age and condition factor improved significantly as lake sturgeon aged, although TOG remained a poor indicator of the differences in condition at age among sturgeon populations. As elsewhere in the literature, declines in length and weight at age occurred at higher latitudes. However, growth rates (mm/degree-day), when adjusted for TOG, showed a significant inverse relationship between growth rates and latitude. The latitudinal countergradient in growth rates partially compensates for reduced growth opportunities in northern populations of lake sturgeon.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0549:LVILSS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We used otolith banding patterns formed during incubation to discriminate among hatchery- and wild-incubated fry of sockeye salmonOncorhynchus nerkafrom Tustumena Lake, Alaska. Fourier analysis of otolith luminance profiles was used to describe banding patterns; the amplitudes of individual Fourier harmonics were discriminant variables. Correct classification of otoliths to either hatchery or wild origin was 83.1 % (cross-validation) and 72.7% (test data) with the use of quadratic discriminant function analysis on 10 Fourier amplitudes. Overall classification rates among the six test groups (one hatchery and five wild groups) were 46.5% (cross-validation) and 39.3% (test data) with the use of linear discriminant function analysis on 16 Fourier amplitudes. Although classification rates for wild-incubated fry from any one site never exceeded 67% (cross-validation) or 60% (test data), location-specific information was evident for all groups because the probability of classifying an individual to its true incubation location was significantly greater than chance. Results indicate phenotypic differences in otolith microstructure among incubation sites separated by less than 10 km. Analysis of otolith luminance profiles is a potentially useful technique for discriminating among and between various populations of hatchery and wild fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0559:DAPOSS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We demonstrate temperature-influenced increment spacing in the sagittal otoliths of juvenile Atlantic menhadenBrevoortia tyrannusreared at different temperatures and describe otolith increment patterns from wild juveniles born in different months. Tank-reared individuals completed metamorphosis a month earlier at 25°C than at ambient temperatures (10–14°C). We identified several patterns from the sectioned otoliths, including reduced time to metamorphosis, faster transition to the juvenile stage, and increased increment spacing after onset of metamorphosis for those individuals exposed to warmer temperatures. For wild individuals that could be accurately aged, mean otolith increment spacing in the zone from 70 to 80 increments increased 1–2 μm for fish born in November and December to more than 3 μm for fish born in February. The increase in increment spacing is consistent with the arrival of individuals across seasonally warming temperatures in the estuary. A discriminant analysis based on otolith increment spacing and metamorphic patterns successfully classified birth month for 59–100% (65% overall) of Atlantic menhaden spawned between November–February. This approach is being developed ultimately to identify the birth month of wild Atlantic menhaden adults in order to test for differential survival among cohorts born in different months that recruit to the fishery.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0579:TEOOMA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The mitochondrial DNA (mtDNA) control region of common snookCentropomus undecimaliswas investigated for its potential use as a genetic mark or “tag” for evaluating eventual stock enhancement efforts for this species. In addition, the general feasibility of recovering and recognizing a genetic tag from an enhanced wild population was evaluated. Snook mtDNA purified from ripe ovary tissue by ultracentrifugation in CsCl gradients was restriction mapped, and the control region was cloned and sequenced. When different clones from the same fish were compared, the control region was found to contain variable numbers of a 39-base pair (bp) tandemly repeating sequence beginning 26 by from the transfer RNA gene for proline. Further evidence of this variation in repeat number was observed between individuals after comparison of polymerase chain reaction (PCR) products obtained from this region by using native mtDNA preparations. Following the repeats was a nonrepeating sequence of 701-bp in which two distinctive sequences were seen among snook from Tampa Bay. The sequences were such that 406-bp PCR products of the two were each distinguishable after digestion with eitherRsaI orTaqI followed by agarose gel electrophoresis. In testing the general feasibility of a rapid, nondestructive, tag “recovery” protocol, mtDNA extracted from small fin clips from 1,425 individual wild-caught snook was used as a template for PCR amplification of the sequence. Of 882 successful PCR amplifications, 789 digests byRsaI plus 500 byTaqI were clearly scored by simple visual inspection of ethidium-stained agarose gels. Only one of the two sequences was further observed in this number of fish from Tampa Bay. The results highlight the specificity of an mtDNA sequence assay in recognizing a specific haplotype and also demonstrate the feasibility of scanning hundreds of fish for a particular mtDNA sequence that might serve as a genetic tag in hatchery-released fish. We also concluded that the mtDNA control region alone in snook might not contain enough sequence variability within a local population to fully exploit the potential of genetic tagging and that other regions of the mtDNA should be investigated.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0594:MDCROC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Many estuaries exhibit seasonal pulses of phytoplankton and zooplankton production. Larval fishes that co-occur with these “blooms” should be at a growth and survival advantage compared with larvae that occur before or after the bloom, although this has been difficult to observe in many systems. We tested this potential advantage for larval (< 10 mm notochord length) striped bassMorone saxatilisand white perchM. americanain the Hudson River by examining consumption and feeding selectivities with respect to zooplankton blooms. The cladoceranBosmina longirostrisand large copepodite and adult copepods together composed 97.4%, and 90.9% of larval striped bass and white perch diets, respectively. Peak consumption rates ofBosminacoincided with the bloom. whereas copepod consumption rates continued to increase throughout the sampling period. Selectivity for copepods was inversely related to selectivity forBosminaand was high, except at those sites and times whenBosminadensities exceeded 14 animals/L. Per capita energy consumption was highest (0.75 and 0.39 Rindividual for striped bass and white perch, respectively) after the bloom period, but specific consumption (energy consumed/mg wet weight fish) during and after the bloom were similar (2.39 versus 2.35 J/mg dry weight during the bloom versus after the bloom for striped bass and 2.58 versus 2.63 Ping for white perch). Our energetics analyses indicate that different-sized fish experience different benefit–cost (consumption benefit : respiration cost) ratios, but strong trends exist with respect to the zooplankton bloom. Prebloom cohorts have the least available food and lowest metabolic costs (respiration). Postbloom cohorts have both high consumption and respiration rates due to increased temperatures. Cohorts coincident with the bloom have moderately high specific consumption rates and lower metabolic costs relative to late cohorts. We conclude that larval cohorts coincident with the bloom possess an energetic advantage relative to early cohorts but not relative to late cohorts.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0607:CSAUOZ>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Available prey influence fish recruitment, especially when size-dependent processes, such as starvation or predation, dictate larval survival. Yet, for zooplanktivorous larval fishes. quantitative assessments of how zooplankton density and quality (i.e., size or taxonomic composition) influence foraging success, growth, and survival are rare. With small-scale experiments, we tested whether high densities of small zooplankton promote recruitment of age-0 gizzard shadDorosonia cepedianumfrom the larval (<25 mm total length, TL) to the juvenile (≥25 mm TL) stage. In our first experiment, in which larval and early juvenile gizzard shad (10–29 mm TL) were exposed to a range of densities of small zooplankton, foraging success varied substantially but generally increased at zooplankton densities over 200/L for larvae less than 20 mm TL and at densities over 100/L for individuals 20 mm TL or longer. In a second experiment. larval gizzard shad (15 mm TL), after 2 weeks in 1-m3enclosures, survived more than 300% better in enclosures containing small zooplankton (mean = 0.33 mm) than in enclosures containing large zooplankton (0.39 mm), even though growth was similar between treatments. In a third experiment, early juveniles (24 mm TL), after 2 weeks in 1-m3enclosures, grew significantly faster, but survived no better, in high (600 zooplankton/L) than low (90 zooplankton/L) densities of small zooplankton. Interactions among zooplankton size, zooplankton density, and gizzard shad size early in life should strongly affect larval gizzard shad success, which in turn should mediate their impact as juveniles on reservoir zooplankton assemblages and ultimately on fish communities.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0622:EAOTIO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Eight hundred twenty nine yellow-phase American eelsAnguilla rostrata, 160–740 mm total length (TL), were electrofished from 10 stations in the Annaquatucket River, Rhode Island. The eels were individually marked with liquid-nitrogen-cooled brands and released at the site of collection. Resampling yielded 200 recaptures (24%); eels were recaptured at 8 of the 10 stations after 1 year. Of all recaptures, 174 (87%) were from the station of release, indicating restricted movement by American eels from the collection sites. Stations associated with dams had higher recapture rates, but there was no significant relationship between percent recaptured and eel density, station size, or distance upriver. An annual growth rate (mean ± SE) of 29.9 ± 4.7 mm/year for all American eels was estimated for a 214-d growing season. The growth rate for eels longer than 399 mm TL, which have previously been shown to be female, was 62.10 ± 14.9 mm/year, 2.3 times greater than for eels less than 400 mm. Mean growth rates do not appear to be a function of distance upriver or density but are more closely related to the sex ratio of eels at the station. Comparison of these growth rates with other published growth rates suggests that both sex ratio and latitude are important factors influencing the growth rate of a given population.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0638:MAGROY>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We tested the hypotheses that the incidence of metamorphosis in sea lampreysPetromyzon marinusis related to the magnitude of the spring rise in temperature and that high larval density prior to metamorphosis reduces the number of animals entering metamorphosis. Concurrently, we also tested the accuracy of predicting metamorphosis based on minimum size criteria of 120 mm and 3.0 g and condition factor (CF) of 1.45 for larval data collected in the fall, where CF = 106(mass, g)/(total length, mm)3. The spring rise in temperature was a critical step in stimulating metamorphosis, but neither the magnitude of warming in the spring nor larval density significantly affected the proportion of metamorphosing animals. By using a CF of 1.45 or greater as the criterion for larval data collected in fall, we predicted 92% of the metamorphosis that occurred the following summer. Predictions of sea lamprey metamorphosis based on fall data were as accurate as predictions made in previous studies that examined spring data and used minimum size criteria of 120 mm and 3.0 g and a CF of 1.50 or greater. The equal success of using a CF of 1.45 or greater with fall data and a CF of 1.50 or greater with spring data might have reflected that some lipid accumulation occurs between the fall and the onset of metamorphosis the following July.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0647:LSOTEO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The magnitude of biases introduced into population estimates by the varying catchability of fish was observed by employing several strategies for estimating population sizes of northern pikeEsox luciusin six north-central Minnesota lakes. The strategies relied on commonly used sampling techniques for northern pike and differed in the degree to which they addressed differences in catchability among fish. Biases were measured as percent differences among population estimates. Estimates of known populations of tagged fish showed that the Petersen technique, which incorporated independent gear types for marking and recapture, was relatively unbiased. Biases from differences in catchability due to fish size were small. In contrast, large biases from differing fish behaviors and habitat uses were found in removal or multiple mark–recapture methods. Both method types relied on sampling nearshore movements of northern pike during early spring, and both severely underestimated population sizes. Removal estimates were lower than the number of fish actually caught, and multiple mark–recapture estimates averaged 39% lower than Petersen estimates. These results suggest that population estimates derived by sampling a fish behavior pattern (such as nearshore spring movements of northern pike) may not be valid. The assumption of equal catchability during such movements was very sensitive. Violations of this assumption caused critically large differences in population estimates for northern pike.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0658:VCABIP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We measured or described microhabitat characteristics of woody debris accumulations (i.e., structural complexity, cavity space, stein diameter, suspended and benthic leaves, depth, inside and outside flow, undercut bank, and lateral position) found in headwater coastal plain streams of central Louisiana. Debris characteristics at sites used as diurnal cover by adult brown madtomsNoturus phaeusand pirate perchAphredoderus sayanuswere compared with characteristics at unoccupied debris sites. Woody debris used by brown madtoms was characterized as having greater cavity space, structural complexity, and suspended leaves. Additionally, brown madtoms more frequently occupied debris areas located beneath undercut banks or next to areas of high flow. Of all the habitat variables, undercut bank and cavity space showed the strongest relationship with the presence of brown madtoms in woody debris. Brown madtoms demonstrated no significant difference in use of debris characteristics between small (34–83 mm TL), medium (84–101 mm TL), and large (102–140 mm TL) size-groups. Relative to unoccupied sites, pirate perch more frequently occupied sites with benthic leaves and leaves suspended within the debris. Debris in deep water with undercut banks and slow inside flows were also used more by this species regardless of its size-group. The structural complexity of debris at sites occupied by large and medium size pirate perch (59–95 mm TL) was significantly greater than that at unoccupied sites and at sites occupied by small pirate perch (27–58 mm TL). Overall, submerged debris tended to have specific physical characteristics that acted as important determinants in diurnal habitat use of these two structure-associated fishes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0665:COWCUB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor