摘要:

I calculated the relationship between instantaneous natural mortality,M(d–1), and dry body weight,W(μg) for herring larvae and adults using data from the scientific literature. Geometric mean mortality of adult Pacific herringClupea pallasi(0.52·year–1) was about three times greater than that of adult Atlantic herringClupea harengus(0.18·year–1), which may reflect greater reproductive effort per unit size by Pacific herring than by Atlantic herring. Geometric mean mortality of Pacific herring larvae (0.083·d–1) was 30% greater than that of Atlantic herring larvae (0.064·d–1), but the difference was not significant. The functional regression for Atlantic herring was loge(M) = –0.4924 – 0.4064·loge(W), and the regression for Pacific herring was loge(M) = 0.1553 – 0.3935·loge(W). The regressions provide preliminary estimates of averageMof herring eggs and juveniles, life history stages for which there are few direct estimates of mortality. They also indicate that the weight exponent of instantaneous growth of herring should be greater than –0.4. Allometry of herring mortality implies that year-class strength of herring should be positively correlated with size at recruitment.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1035:AOHM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fish communities in acidic lakes of New Jersey have fewer species than do those in more alkaline lakes of comparable size. This conclusion is based on a multiple regression analysis of published data on fish communities, area, and pH in 85 lakes. Some interesting patterns emerge, however, when species are partitioned into introduced and native species. As expected, diversity of introduced species declines with increasing acidity. The number of native species in a particular lake, however, is independent of pH (range of 4.1 to 9.1). Although diversity of native species is not influenced by pH, species composition changes. The lack of a significant relationship between species diversity of native species and pH can be attributed to the replacement of acid-intolerant species by tolerant species. The smaller number of introduced species in acidic lakes is attributable to both fewer species stocked and a greater frequency of failure for those that were stocked. Species introduction records for largemouth bassMicropterus salmoidesand bluegillLepomis macrochirus, which are not native to New Jersey, reveal far more failed introductions in acidic waters than in neutral or alkaline waters.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1043:SDOFIN>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Bioenergetics modeling was used to quantify the consumption dynamics of lake troutSalvelinus namaycushin Flaming Gorge Reservoir, Utah–Wyoming. Analysis of diet and population estimates of different size-classes of lake trout indicated that kokaneesOncorhynchus nerkamade up the greatest proportion of prey biomass. Examination of growth rates of forage fish and predator–prey size ratios indicated that Utah chubGila atrariawere more vulnerable than kokanees to lake trout predation. Utah chub grow slower than kokanees and thus were susceptible to piscivores over a longer age span. We conclude that kokanees will make up an even larger proportion of the pelagic fish assemblage of Flaming Gorge Reservoir in future years.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1058:LTCARC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Factors that affect recruitment of threadfin shadDorosoma petenenseand gizzard shadD. cepedianum, two important prey species in southern reservoirs, are not well understood. Larval shad typically have not been identified to species, though interactions between shad larvae likely affect their recruitment and that of their predators. Using myomere counts to identify larval shad to species, we quantified spatial and temporal variation in species distributions in West Point Reservoir, Alabama–Georgia. We sampled larvae every 3–4 d at three distances from shore (inshore and 25 and 50 m offshore) at each of three sites. Larval threadfin shad migrated offshore in all three sites, whereas larval gizzard shad were evenly distributed across distances from shore. Because of these movement differences, larval gizzard shad and larval threadfin shad may encounter different habitat-specific predation rates, climatic effects, and food availability. In addition, larval gizzard shad were present before larval threadfin shad and grew beyond the size vulnerable to our capture techniques before threadfin shad abundance peaked. If zooplankton densities are reduced by young-of-year shad, as documented in other systems, later-hatched threadfin shad would encounter fewer zooplankton than were available to the earlier larval gizzard shad. Threadfin shad would have reduced growth and greater vulnerability to predation and starvation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1070:SATHOL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We estimated the growth and mortality of larval sunfishLepomisspp. in backwater habitats of the upper Mississippi River with an otolith-based method and a length-based method. Fish were sampled with plankton nets at one station in Navigation Pools 8 and 14 in 1989 and at two stations in Pool 8 in 1990. For both methods, growth was modeled with an exponential equation, and instantaneous mortality was estimated by regressing the natural logarithm of fish catch for each 1-mm size-group against the estimated age of the group, which was derived from the growth equations. At two of the stations, the otolith-based method provided more precise estimates of sunfish growth than the length-based method. We were able to compare length-based and otolith-based estimates of sunfish mortality only at the two stations where we caught the largest numbers of sunfish. Estimates of mortality were similar for both methods in Pool 14, where catches were higher, but the length-based method gave significantly higher estimates in Pool 8, where the catches were lower. The otolith-based method required more laboratory analysis, but provided better estimates of the growth and mortality than the length-based method when catches were low. However, the length-based method was more cost-effective for estimating growth and mortality when catches were large.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1080:GAMOLS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We used biotelemetry to study the movements of 23 adult shortnose sturgeonsAcipenser brevirostrumand 23 subadult Atlantic sturgeonsAcipenser oxyrhynchus oxyrhynchusin the lower 46 km of the Merrimack River between 1987 and 1990. Shortnose sturgeons used two freshwater reaches and one saline reach annually. Sexually mature fish began moving upriver from freshwater wintering areas to a spawning site in April, when increasing river temperature reached about 7°C and decreasing river discharge reached about 570 m3/s. Following spawning in late April–early May, fish moved downriver either to a freshwater reach where they remained all year or farther downriver to a saline reach where they remained for up to 6 weeks. After fish used the saline reach, they returned upriver to fresh water. Atlantic sturgeons entered the river from coastal waters by mid–late May, when increasing river temperatures reached 14.8–19.0°C and decreasing river discharge reached 303–675 m3/s, occupying a saline reach with 0.0–27.5‰ salinity. After using the same saline reach visited briefly in spring by shortnose sturgeons, Atlantic sturgeons emigrated from the river by October when maximum river temperatures were 13.0–18.4°C. We observed no tagged Atlantic sturgeons in the river in successive years. Except for use of the saline reach during spring, the two species were spatially separate.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1088:AMOSAA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We determined the prolonged swimming performance of two size-classes of northern squawfishPtychocheilus oregonensisat 12 and 18°C. The percentage of fish fatigued was positively related to water velocity and best described by an exponential model. At 12°C, the velocity at which 50% of the fish fatigued (FV50) was estimated to be 2.91 fork lengths per second (FL/s; 100 cm/s) for medium-sized fish (30–39 cm) and 2.45 FL/s (104 cm/s) for large fish (40–49 cm). At 18°C, estimated FV50 was 3.12 FL/s (107 cm/s) for medium fish and 2.65 FL/s (112 cm/s) for large fish. Rate of change in percent fatigue was affected by fish size and water temperature. Large fish fatigued at a higher rate than medium-sized fish; all fish fatigued faster at 12 than at 18°C. The mean times to fatigue at velocities of 102–115 cm/s ranged from 14 to 28 min and were not affected by fish size or water temperature. Our results indicate that water velocities from 100 to 130 cm/s may exclude or reduce predation by northern squawfish around juvenile salmonid bypass outfalls at Columbia River dams, at least during certain times of the year. We recommend that construction or modification of juvenile salmonid bypass facilities place the outfall in an area of high water velocity and distant from eddies, submerged cover, and littoral areas.

ISSN:0002-8487    

DOI:10.1577/1548-8659(0)122<1104:PSPONS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We evaluated analytical approaches to discriminating littoral fish assemblages with catch data from multiple sampling gears. Eight littoral sites were sampled with seines, fyke nets, and gill nets in Lake Mendota, Wisconsin, in summer 1990. No one gear sampled the full composition represented by the total catch. Fyke nets best discerned differences among littoral fish assemblages. Young-of-year (age-0) bluegillsLepomis macrochirusand age-0 black crappiesPomoxis nigromaculatuscaught in the fyke nets were the strongest discriminators among sites. Gill nets did not differentiate among sites. With the seine and fyke net, analysis of absolute abundance data detected differences among sites; analysis of presence–absence and rank abundance data did not. Fish caught in fyke nets were the most frequent significant correlates in site ordinations based on log-abundance data for taxa, defined as a combination of species, age (age 0 or adult) and gear type. Retention of gear designation in site ordination attributes facilitated the assessment of gears for differentiating littoral fish assemblages.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1111:AFDLFA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Two experiments were conducted with rainbow troutOncorhynchus mykissto investigate the influence of several diets and supplemental phosphorus on discharges of phosphorus in hatchery effluent water. A diet was formulated to contain no fish meal and a reduced level of non-phytin phosphorus (approximately 0.9%) provided, in part, by supplemental defluorinated rock phosphate, which has a low solubility in water. Feeding rainbow trout this diet supported 86% of the growth attained with a conventional hatchery diet while discharges of phosphorus in the effluents decreased by 40–51%.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1120:IOPIRT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The stress of routine transport practices on hatchery-reared brook troutSalvelinus fontinalis, lake troutSalvelinus namaycush, and splakeS. fontinalis×S. namaycushwas evaluated by measuring changes in plasma levels of the stress hormone cortisol, the key stress metabolite glucose, and the plasma electrolytes Na+and Cl–, and by measuring net ion and ammonia exchanges with the water in the transport tanks. We examined actual transport trips and standardized net confinement stress in the laboratory to quantify differences in stress response among the species. Brook trout were the least sensitive to both transport stress and net confinement, and responded in a similar fashion to both treatments. Splake responded to transport like brook trout but were the most sensitive to net confinement. Species differed most in their ability to maintain ion exchanges with the water under stress. Lake trout experienced ion losses during transport that were about 10-fold higher than losses from brook trout and splake. Trip duration (3.5–11 h) had only a minor effect on physiological responses, and wide variations in loading density (6.9–17 kg/100L) had no significant effect. Increasing O2levels in the water (due to oxygenation rather than aeration of the tanks) proved to be moderately stressful to brook trout, based on elevations in plasma cortisol levels. Our results permit an evaluation of the relative contributions of different transport variables to the transport stress imposed on salmonids.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<1127:ROHRBT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor