摘要:

Standing stocks (kg/hectare) of channel catfish Ictalurus punctatus were graphed against 19 abiotic variables measured for Kansas streams. The resulting habitat suitability curve for each variable allowed fish biomass to be normalized to index values (range, 0.0–1.0) that could be regressed linearly against the abiotic variables. Stepwise multiple-regression techniques isolated three variables (runoff, fraction of stream area consisting of runs, and water temperature) that accounted for nearly half the variability in channel catfish biomass. When the regression model derived from Kansas data was applied to an independent data set from Oklahoma, the correlation between predicted and observed standing stocks was highly significant, though low. Assigning suitability index values to the Oklahoma data set from the habitat suitability curves developed from Kansas data resulted in a significant model with more (often different) variables accounting for three-fourths of the biomass variability. The regression model must be fit separately to each data set; although it is locally useful, it has low predictive power across geographic regions. It does indicate (a) that habitat suitability curves are at least regionally consistent, and (b) that variations in stream biomass of channel catfish can be explained largely in abiotic terms.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<771:RBHVAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Allele frequencies for wild rainbow trout Salmo gairdneri from the upper Yakima River and two tributary creeks were intermediate between those for introduced hatchery populations and those for inland populations native to other areas of the Columbia River basin. Previously published results had demonstrated a widespread geographic consistency in allele frequencies at two loci among both anadromous and nonanadromous populations in the Columbia River drainage east of the Cascade Mountains. The intermediate allele frequencies at these two loci for rainbow trout from the upper Yakima River, therefore, suggest that these populations represent genetic admixtures of native and nonnative stocks. Allele frequencies at several other loci plus field surveys of spawning fish further suggest that nonanadromous rainbow trout from domesticated hatchery strains, rather than hatchery-reared steelhead (anadromous S. gairdneri), have been responsible for the suspected introgression of nonnative genes into the Yakima River populations. We hypothesize that nonanadromous rainbow trout of hatchery origin may have survived and reproduced in relatively large numbers in the upper Yakima River because of major declines in the abundance of native steelhead and of two indigenous species of Pacific salmon Oncorhynchus sp.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<782:EEFAGA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Chemosensory cues, particularly those emanating from substrate areas occupied by previously hatched young, may play an important role in the reproductive behavior of lake trout Salvelinus namaycush. Support for this hypothesis was obtained in laboratory experiments. Adults were placed in a large circular pool with four experimental reefs. Egg membranes and feces obtained from young that had hatched earlier were placed in polyester fiber in screen envelopes and positioned on selected reefs. Females approached and males contacted (“cleaned”) the treated reefs but not the untreated reefs. Of 6,858 eggs recovered, 92% were from treated reefs. Some of these eggs had been fertilized and provide the first record of volitional spawning by lake trout under artificial conditions. A second experiment was less definitive, because no spawning occurred, but visual observations and analysis of videotaped behavior sequences showed that, again, adults were attracted more to reefs treated with feces of young of the year than to untreated reefs.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<794:LTRB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Several measures of the size composition of spawning substrates were used to describe the survival of preemergent embryos of rainbow trout Salmo gairdneri in a groundwater-fed streambed. Survival was not significantly related (P > 0.05) to the percentage of sediments smaller than 2.0 mm in diameter, the geometric-mean particle size, or fredle indices of substrate quality. However, survival strongly depended on the mean dissolved oxygen content and velocity of groundwater in redds. Dissolved oxygen concentrations were not related (P > 0.05) to measures of substrate size composition, and these variables accounted for only a limited proportion of the variance among redds in seepage velocities. These factors account for the lack of any significant association between survival and substrate size composition. The findings of this study imply that embryo survival models based on substrate size composition may not be entirely suitable for assessing the quality of spawning beds in groundwater-fed streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<804:PORTES>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Movements of shortnose sturgeon Acipenser brevirostrum, an endangered species, were studied for 5 years by radio telemetry and mark-recapture in the lower 140 km of the Connecticut River to Long Island Sound. Ninety fish (range, 54–97 cm fork length; 1.2–9.2 kg weight) were equipped with radio transmitters. The cycle of annual movement consisted of several up- and downriver migrations between four discrete areas that were used for summer feeding, spawning, and over-wintering. Thus, the major portion of the river served as a conduit for movement between the areas of major use. Each year, some adults remained in fresh water. Yearly movements were complex; fish of different age classes and reproductive conditions associated seasonally in the same habitat.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<813:YMOSSI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Capture-recapture methods were used to estimate the population size and density of American eels Anguilla rostrata in a 1-km section of a tidal creek during May. Of 645 American eels tagged over 6 d, 282 were recaptured at least once. Adjusted Petersen, Schnabel, and computer-modelling techniques produced population estimates ranging from 728 to 928 American eels, corresponding densities being 182–232 fish/hectare, and an approximate biomass of 50.5 kg in the 4-hectare study site. Capture location records indicated a mean home range of 1.04 hectares for 82 American eels recaptured two or more times. Combined with other short- and long-term observations, American eels at this estuarine site appear to exhibit relatively restricted movements.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<821:PSAHRO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Water quality effects of high densities of silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella, and water hyacinths Eichhornia crassipes in semi-intensive pond culture of prawns Macrobrachium rosenbergii were examined. Additional effects of isonitrogenous additions (8 kg N˙hectare−1˙week−1) of dried chicken manure and chicken broiler feed were evaluated. Excretion, grazing, and sediment resuspension by the carps stimulated phytoplankton productivity and turnover rates of microplankton, led to high early-morning dissolved oxygen (DO) concentrations, and, in the ponds fed manure, increased phytoplankton biomass. Removal of phosphorus from the water by water hyacinths led to reduced chlorophyll-α concentrations, primary productivity, and microplankton turnover, and to low morning DO concentrations: In hyacinth ponds fed chicken broiler feed, there were large percentage fluctuations in phytoplankton biomass. Additions of manure stimulated autotrophic productivity about 3.0 times, and total microbial productivity about 4.6 times, more than additions of chicken feed. Biological control of phytoplankton dynamics and maintenance of DO concentrations at high phytoplankton standing crops by Chinese carps appears a viable alternative to present methods of water quality control in semi-intensive prawn aquaculture.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<826:EOPAMF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We collected 1,351 male and 632 female tilefish Lopholatilus chamaeleonticeps off Georgia with bottom longlines between May 1982 and August 1983. Anal fin rays formed a single annulus yearly between May and October. Tilefish reached 33 years of age and growth of males was significantly faster than females. Length-frequency histograms indicated that exploitation had not yet truncated the size structure of this substock. Males were fully recruited to the fishery at age 12 (mean standard length 606 mm) whereas females were fully recruited at age 10 (mean standard length 525 mm). Three estimates of instantaneous total mortality ranged from 0.10 to 0.25; most of this was attributable to natural mortality. Because these fish are long-lived and slow-growing and possess low natural mortality rates, they are vulnerable to overexploitation by a relatively low fishing effort. Consequently, fishing effort may have to be tightly regulated if optimal yields are to be sustained in this fishery.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<837:GMAACO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Otoliths from 1,291 Atlantic croakers Micropogonias undulatus, with total lengths from 113 mm to 417 mm, from the northern Gulf of Mexico were examined to determine age and growth. Marginal increment analysis was used to determine that otolith marks formed annually. Ages ranged from 0 to 8 years. No significant difference was found for length at age between males and females. The von Bertalanffy equation was Lt= 419.2[1 - e−0.273(t+1.405)], where Lt= total length (mm) and t = age (years). The length-weight relationship (r = 0.99) was W = 5.302 × 10−6TL3.134where W = weight (g) and TL = total length (mm).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<847:AAGOAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The relationship between catch and trawling effort was explored for Penaeus aztecus, P. setiferus, and P. duorarum. Tow durations of 5, 10, 15, 20, 25, and 30 min bottom time were examined, and data were analyzed with orthogonal polynomials in a randomized complete block design. We found a significant linear relationship between catch and tow duration, which is consistent with the assumption of a constant catchability coefficient. However, tow duration accounted for only a small proportion of the total variation in catch. This indicates that catch-per-unit-effort indices of abundance may be improved when analyzed in statistical designs that consider other sources of variation in catch in addition to fishing effort. Scaling of catch data when tow durations vary is briefly discussed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<851:RBTCAT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor