摘要:

An age-structured production model of multicohort fish population dynamics based on the mean metabolic state of individuals and the average abundance of year-classes is proposed. The model allows variations in life stage basal metabolic rates by parameterizing their effects on total population abundance through a mortality function which itself depends upon an individual's status relative to an optimal metabolic state. The metabolic equations are derived in terms of age-specific individual weight. The interaction of individual status and intraspecific competition is allowed by coupling the metabolic equations for growth to those for population abundance. This coupling yields a second-order nonlinear equation in abundance or biomass. In model simulations, (1) increased numbers of cohorts decreased the stability of population biomass, (2) numerically “strong” year-classes damped and sometimes caused collapse of proximal age-classes, (3) exploitation reduced competitive interactions and increased model stability, and (4) increases in natural mortality introduced greater recruitment variability. The transitional and steady state behaviors of the multicohort model are explored and compared to traditional fishery management models for a small pelagic species, northern anchovyEngraulis mordax.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0343:AMSPM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

One of the few remaining fisheries for Atlantic sturgeonAcipenser oxyrinchustakes place during spring and fall in the New York Bight, but no information on the stock composition of this fishery is available. We used data from mitochondrial DNA (mtDNA) restriction fragment length polymorphism analysis to estimate the relative contributions of source stocks of Atlantic sturgeon to a New York Bight fishery sample (N= 112) collected in 1993 and 1994. Composite mtDNA haplotype frequencies of source populations were first characterized with five informative restriction enzymes:BglI,MspI,EcoR V,Hinf I, andHincII. All St. Lawrence River, Quebec, and St. John River, New Brunswick, specimens had an identical haplotype (genotypic diversity = 0.0); for the purposes of mixed-stock analysis, both populations were pooled as the “Canadian stock.” Genotypic diversity ranged between 0.483 and 0.750 among samples from the Hudson River in New York, the Edisto River in South Carolina, and the Ogeechee, Altamaha, and Satilla rivers in Georgia. Chi-square analyses indicated that the Edisto, Savannah (Georgia), Ogeechee, Altamaha, and Satilla River samples should be grouped as the “southeastern stock,” and that haplotype frequencies of the three source stocks (Canadian, Hudson River, southeastern) were highly heterogeneous (P= 0.0000). Mixed-stock analysis with a constrained least-squares approach under the conditional method indicated a 97.2% Hudson River contribution, a 2.8% contribution by the southeastern stock, and a 0.0% contribution by the Canadian stock; the unconditional method provided estimates of 99.1%, 0.9%, and 0.0%, respectively. Frequencies of mtDNA haplotypes of subadults (N= 30) from a seasonal aggregation of Atlantic sturgeon from the lower Delaware River were intermediate between those of the Hudson River and southeastern stocks. This finding, together with ancillary information, suggests that the Delaware River aggregation is primarily either a mixture of both the Hudson River and southeastern stocks or of the Hudson River stock and a relict Delaware River stock.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0364:SCOTNY>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We analyzed allozymes from 13 collections of lingcodOphiodon elongatusrepresenting over 1,100 individuals throughout most of the species' range from Alaska to central California. Data were gathered from 41 presumptive gene loci of which 19 loci (46%) were polymorphic (P0.99criterion, whereby the frequency of the most common allele is 0.99 or less in at least one collection). Average observed heterozygosity was 0.050 (SE, 0.001). Significant differences in genotype frequencies were found between sexes at theAH-2*locus for aconitate hydratase. Although lingcod populations are genetically similar throughout the range, significant allele frequency differences suggest that lingcod in Puget Sound are partially isolated from those along the open coast.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0372:GVAPSO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Native trout populations throughout western North America have declined because of habitat alteration, introgression with introduced trout, or competitive exclusion by nonnative species. Consequently, identification and preservation of native trout are now the goals of many management programs. We examined allozyme and mitochondrial DNA (mtDNA) variation in seven naturally occurring populations and one hatchery population of rainbow troutOncorhynchus mykissfrom southern Idaho and northern Nevada to determine their genetic origins. Allozyme and mtDNA results were concordant in identifying three populations as genetically pure interior rainbow trout and one population as a hybrid swarm. Results for the remaining four populations were discordant. However, these latter four populations were best classified as hybrid swarms due to the nature of either the allozyme or mtDNA data, which included genetic characteristics of both coastal and interior rainbow trout. Our study demonstrates the utility of mtDNA analysis in conjunction with independent criteria such as allozymes for detecting hybridization at the population level. Hybridized populations exhibited a greater number of mtDNA haplotypes than did genetically pure populations. Haplotypes within hybridized populations differed more from one another than did mtDNA haplotypes within nonhybridized populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0387:GDOPHB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We conducted laboratory evaluations of food consumption, growth, and metabolic rate as functions of water temperature (5–27.5°C) to examine how the young of year in six populations of muskellungeEsox masquinongy(Kentucky, Minnesota, New York, Ohio, St. Lawrence River, and Wisconsin) from three drainages might perform under various thermal regimes. Relative food consumption (g·g−1·d−1) and growth (g·g−1·d−1) were similar among populations at lower temperatures (5 and 10°C, but at higher temperatures (15–27.5°C) fish from Wisconsin and Ohio had higher consumption and faster growth rates than fish from Kentucky and the St. Lawrence River. Metabolic rates increased with temperature from 0.08 mg O2·g−1·h−1at 5°C to 0.25 mg O2·g−1·h−1at 25°C, but few differences in metabolic rates were observed among populations at any temperature. Although we found bioenergetic differences among muskellunge from these populations, they could not be explained solely in terms of thermal adaptation or previously defined genetic groupings. Energetic differences among age-0 muskellunge have important implications for conserving existing esocid populations and managing introduced populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0402:COFCGA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Young gizzard shadDorosoma cepedianumcan have dramatic effects on ecosystem structure because their high consumptive demand can eliminate crustacean zooplankton populations. The objective of this study was to examine diel feeding chronology of age-0 gizzard shad (25–89 mm total length), as well as their daily ration and consumption ofDaphniaspp., in Oneida Lake during 1991 and 1992. Gastric evacuation titres, treasured experimentally, were faster for fish fed continuously (0.8–1.8 h) than for fish fed single meals of zooplankton (4.0–7.2 h) and were influenced by fish size. In Oneida Lake, young gizzard shad exhibited a diel feeding cycle; gut fullness gradually increased to a maximum during 1100–1900 hours and declined during the night. Juvenile gizzard shad shifted from a diet of exclusively zooplankton in July to a combination of zooplankton, algae, and detritus in August. Estimates of total daily ration ranged from 1.2 to 21.3% of wet body weight, and total daily ration of young gizzard shad increased with fish size. Our estimates of daily ration, based on fish feeding continuously during the day and digesting a single meal at night, closely approximated the maximum daily field ration of age-0 gizzard shad in Oneida Lake. TheDaphniapopulation in Oneida Lake collapsed during July 1991, andDaphniaconsumption by gizzard shad dropped sharply with it; from dietary considerations, the collapse could have been caused by a density of approximately 300,000 age-0 gizzard shad per hectare. In 1992,Daphniaproduction remained strong during July and August, andDaphniaconsumption by gizzard shad did not decline. Because young gizzard shad can switch from zooplankton to phytoplankton as an alternative food source, we hypothesize that gizzard shad have a greater influence on growth and survival of age-0 yellow perchPerca flavescensthan yellow perch have on gizzard shad, because yellow perch rely more onDaphniaas a primary food.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0411:DFDFIA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We evaluated the effects of stem density on the attraction of bluegillsLepomis macrochirusand largemouth bassMicropterus salmoidesto mats of artificial vegetation in a 5-ha impoundment in southwestern Ohio. We also used field enclosures to examine the effects of artificial vegetation density on growth of age-0 bluegills and on predation risk of age-0 bluegills (< 50 mm total length, TL) from largemouth bass. The densities used were 0 (zero), 400 (low), 961 (medium), and 3,844 (high) stems/m2. Underwater surveys of mats indicated significant differences in numbers of age-0 bluegills among vegetation densities; high-density mats always attracted significantly more age-0 bluegills than other densities. Numbers of larger bluegills (>50 mm TL) were similar among vegetation densities, whereas largemouth bass were more abundant near high-density mats. Lengths of age-0 bluegills did not differ significantly among stem densities, suggesting that selection of cover density did not depend on fish size. In addition, growth of age-0 bluegills over 117 d in enclosures did not differ significantly with respect to stem density. In field enclosures, high-density mats significantly reduced predation risk for age-0 bluegills relative to low- and zero-density mats; predation risk did not differ significantly between high- and medium-density mats. Laboratory experiments indicated no differences in predation rate between zero- and low-density treatments, but predation rates were significantly lower in medium and high stem densities than in low and zero densities, and high-density mats offered significantly greater protection than medium-density mats. This study, together with information from other studies, provides evidence that age-0 bluegills need not sacrifice growth for safety when they select high vegetation density under natural conditions.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0422:EOSDOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Electromyogram (EMG) biotelemetry was used to assess activity patterns for adult free-swimming largemouth bassMicropterus salmoidesand smallmouth bassMicropterus dolomieu. We first conducted laboratory respirometry trials and found a strong association between EMG signal and swimming activity which indicated that EMG biotelemetry could be used to assess activity of wild fish. A field study confirmed that both species exhibit diurnal activity patterns. When EMG activity was compared with estimates of swimming activity from location tracking, elevated EMG activity was often recorded for apparently stationary fish. These observations suggested that fish activity at spatial and temporal scales too small for detection by location tracking may account for a significant proportion of daily activity. We argue that EMG biotelemetry, combined with location tracking, may be a versatile tool for application to a wide variety of problems in fisheries biology, including the study of physiological energetics and spatial and temporal habitat use.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0434:APOLAS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Laterally compressed panfishes are small and have limited intraperitoneal space; thus, they may suffer adversely from surgically implanted transmitters even if the transmitter meets the generally recommended ratio of transmitter weight to fish weight of 2%. We studied the effects of intraperitoneal transmitters (2.81 g) on survival, growth, healing, and health of bluegillsLepomis macrochirus(mean weight 133 g) held for 8 weeks at 6°C and 20°C. Radio-tagged bluegills at 20°C had a mortality rate of 10% and tag loss rate of 15%. At 6°C, bluegills had no mortality or tag loss. Radio-tagged and reference fish fed in both 20°C raceways; however, a few reference fish appeared dominant at feeding time. This dominance by a few reference fish was also indicated by a large weight gain for three reference fish in each 20°C raceway. At 6°C, neither reference fish nor radio-tagged fish fed activity. Radio-tagged fish held at 20°C exhibited pelvic fin erosion, erythema and necrosis at the antenna exit and at suture insertions, and lost or loose sutures, effects not observed in other test fishes. Examination of fish held at 20°C also showed enclosure of the transmitters in a fibrous capsule and adhesion of visceral organs. Epithelialization over the incision occurred in radio-tagged bluegills at both temperatures, but there was little further healing at 6°C. At 20°C, tissue responses included chronic inflammation and dermal granulation. Radio-tagged fish did not appear to be more susceptible than reference fish to bacterial infection. Mortality, adverse morphological effects, altered behavior, and limited healing in blue-gills suggest that implanted transmitters impaired their health. Thus, movement and habitat use data collected by telemetry for this species and perhaps for other panfishes should be interpreted with caution.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0440:EOITOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

During the late 1970s, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) from a chemical plant contaminated sediments and fishes for more than 250 km of Bayou Mete, a warmwater lowland stream in east-central Arkansas. During the mid-1980s, TCDD concentrations ranged as high as 2,500 ppt (parts per trillion, ng/kg) in sediments and 1,900 ppt in fishes, resulting in a limited ban on sportfishing and total ban on commercial fishing in that stream. In 1991, a study was initiated to determine the persistence of TCDD in Bayou Meto fishes and sediments and the extent of its dispersal from the point source. Concentrations of TCDD in food fish fillets exceeded the U.S. Food and Drug Administration's foodstuff levels (25 ppt) for more than 20 km below the point source and young bluegillsLepomis macrochirusand sediments exceeded detectable limits (1 ppt) throughout the river. Highest TCDD concentrations in fish (296 ppt) and sediment (276 ppt) were found immediately below the source, but those levels were lower than concentrations found there in 1982 and 1987. Lipid-corrected values demonstrated no clear biomagnification of TCDD for predatory or older fishes. The apparent decline of TCDD, both over time and distance, has led to reopening the lower reaches of Bayou Meto to commercial fishing.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0450:DAPOTP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor