摘要:

The purpose of this study was to evaluate the impact of the March 1989Exxon Valdezoil spill and subsequent cleanup activities on density, biomass, and species diversity of intertidal fishes in Prince William Sound, Alaska. Intertidal fish were sampled in a quasi-experimental, matched-pairs (oiled–cleaned versus reference sites) design stratified by three habitat types with random selection of oiled–cleaned (O–C) sites. Site pairs were sampled twice in 1990 and in 1991. Of 21 fish taxa, 5 made up 98% and 1 made up 74% of total abundance. There were no significant differences in species diversity between reference and O–C sites. Density, however, was significantly greater at reference sites for all habitats combined for both visits in 1990. In contrast, density in 1991 was about equal at reference and O–C sites. Total biomass for all habitats combined was greater at reference than O–C sites during both visits in 1990, but differences were not statistically significant. In 1991, however, the total biomass at reference and O–C sites was about equal. Forward stepwise multiple logistic regression models indicated that presence of oil was a significant predictor of reduced density at mid-intertidal levels in 1990 but not in 1991. From the general pattern of lower density and biomass on O–C sites in 1990 followed by no significant differences in 1991 and corroborating evidence of multiple-regression modeling, we conclude that the presence of oil and subsequent cleanup activities had a negative impact on intertidal fishes in 1990 and that there was evidence that recovery was underway in 1991.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0461:EOTEVO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Populations of striped bassMorone saxatilisoccur in three regions of Atlantic Canada: the St. Lawrence River and estuary in Quebec; the Gulf of St. Lawrence from Chaleur Bay through Northumberland Strait; and rivers in New Brunswick and Nova Scotia draining into the Bay of Fundy. At least nine rivers are known or believed to sustain spawning populations: the St. Lawrence River (where the spawning stock may be extirpated); the Nepisiguit River in Chaleur Bay; the Tabusintac, Miramichi, Kouchibouguac, and Richibucto rivers in the western Gulf of St. Lawrence; the Saint John and Annapolis rivers in the outer Bay of Fundy; and the Shubenacadie–Stewiacke river system in the inner Bay of Fundy. Historically, commercial striped bass landings in Atlantic Canada were lower than those of the U.S. eastern seaboard, the largest landings being made in New Brunswick. Angling catches are substantial but difficult to verify. Spawning occurs in tidal streams several weeks after ice leaves the system. Adults exhibit regional and long-distance summer migration but seek freshwater refugia for overwintering. Studies of growth, population age structures, comparative total instantaneous mortality rates, meristic and morphometric characters, and parasites, combined with tag returns, strongly suggest that Bay of Fundy rivers, specifically the Annapolis, Shubenacadie, and Saint John, contain stocks that are mixed with U.S. fish in most years. Bay of Fundy fish apparently participate in the striped bass coastal migration on the eastern seaboard, whereas populations in Gulf of St. Lawrence rivers appear to be localized. Anecdotal information from commercial and angling catches suggests more spawning–overwintering populations occur than are known to science. Periodic population assessments should be conducted to provide the information necessary for knowledgeable management of the species in eastern Canada.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0477:LHAPCO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A relative weight approach was used to test the hypothesis that the condition of broad whitefishCoregonus nasusin the Prudhoe Bay region of Alaska increases during the summer feeding season in conjunction with their increasing lipid and protein contents and decreases during winter as fish consume these energy reserves. The conditions of individual fish collected across 12 summer dissection periods from 1988 to 1993 were indexed in terms of their residual values relative to a single whole-population, least-squares regression of loge(weight) against loge(length). Proximate body analyses of lipid and protein contents collected from individual fish across six dissection periods from 1991 to 1993 were also examined. Data pooled for individual year-classes were used to test for increasing mean residual value, mean lipid content, and mean protein content during summer and for decreasing values of each during winter. Of the 68 cases examined (14 year-classes over 6 years), mean residual value changed in the expected direction in 56 instances (P< 3.0 E–7). Of 24 cases in which seasonal changes in lipid and protein contents were available, lipid content changed in the expected direction in 23 instances (P< 3.0 E–6), and protein content changed in the expected direction in all 24 instances (P< 3.0 E–7). Mean residual value changed as expected in all 24 cases. The merits of relative condition-relative weight in the study of fish ecology are discussed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0508:IAICIT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Striped bassMorone saxatilis, bluefishPomatomus saltatrix, and weakfishCynoscion regalisare the dominant piscivores in the Chesapeake Bay. As such, they may influence energy flow in the Chesapeake Bay system according to the prey they eat and the trophic levels at which they feed. We defined and compared the diets of striped bass, bluefish, and weakfish from the Chesapeake Bay, across seasons and early ages. Seasonal weight changes of the predators were used to evaluate how different prey species contribute to the production of average individual piscivores. Dietary overlap among species and across cohorts within a species was low (24–51% bimonthly average range, Schoener's index). Bluefish often had higher dietary overlap values with striped bass and weakfish than with other bluefish cohorts. Dietary overlap between striped bass and weakfish cohorts was usually low because of disparity in the use of bay anchoviesAnchoa mitchilliby striped bass (<31% in all months) and weakfish (>50% for most age-0 and age-1 weakfish). Overall, pelagic prey fishes dominated the diets of all predators except age-0 striped bass, although seasonal differences were evident. During May–June, nearly all predator cohorts fed on benthic prey. In general, the Atlantic menhadenBrevoortia tyrannusand the bay anchovy supported most of the piscivore production, with Atlantic menhaden becoming increasingly important for larger predators. Benthic prey were more important to striped bass (from nearly 100% of diets for age-0 fish in all seasons to 20–100% for older striped bass) and less important to bluefish (70% in July–August, 1–20% at other times and for other cohorts) than was suggested in an earlier food web analysis for the Chesapeake Bay ecosystem.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0520:TRPDAG>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Analysis of data from four extensive fish surveys in the Sacramento–San Joaquin estuary indicated that splittailPogonichthys macrolepidotus, endemic to the Central Valley of California, declined by 62% over a 13-year period. Splittails are now found mostly in the estuary, a fraction of their former range. In a gill-net survey in August 1994, 50% of the splittails taken in the estuary were from the Suisun Bay area, and 50% were just upstream in shallow, well-vegetated areas. Splittails migrate into freshwater to spawn, and river outflow carries juveniles into productive, shallow, low-salinity areas downstream. The high correlation of abundance of young with river outflow (averager2, 0.60) and a weak stock–recruitment relationship (r2= 0.22) indicate that spawning success depends on favorable environmental conditions created by high outflows, such as the number of days that lowland areas remain flooded in the spring. A repeated-measures analysis of variance indicated that splittails prefer shallow, low-salinity habitats. The reductions in splittail abundance and range and the movements and habitat preferences of splittail young and adults correspond to trends and habits of two other species characteristic of the estuary, delta smeltHypomesus transpacificusand longfin smeltSpirinchus thaleichthys. The largest threats to these three species are changes in water management and increases in water diversions that reduce spawning and rearing areas and other low-salinity habitats in Suisun Bay.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0538:SOSITS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Oklahoma streams and reservoirs historically contained only the northern subspecies of largemouth bassMicropterus salmoides salmoides. From 1970 to 1991 Oklahoma reservoirs throughout the state were supplementally stocked with the Florida subspeciesM. s. floridanusand various intergrades of the northern and Florida subspecies. To document the effect of such introductions on the genetic structure of largemouth bass stream populations, largemouth bass throughout Oklahoma were sampled by seining. Electrophoretic analysis was carried out for loci that code the enzymes isocitrate dehydrogenase (sIDHP), aspartate aminotransferase (sAAT-B), and superoxide dismutase (sSOD). These three loci are diagnostic for Florida largemouth bass. Analysis was also carried out for loci that code the enzymes malate dehydrogenase (sMDH-A and sMDH-B), phosphoglucomutase (PGM), and glucose-6-phosphate isomerase (GPI-A and GPI-B). These five loci are known to be polymorphic in largemouth bass. Overall, Florida- subspecific alleles were found in 4% of fish collected and at 11 % of sites that held largemouth bass. Combined frequencies of Florida-subspecific alleles ranged from 0.00 to 0.18; highest frequencies were in the southeastern half of Oklahoma. Overall genetic variability was highest among streams of the Red River basin, andsMDH-B*was the most variable locus. Low meanFstvalues (standardized variances of allele frequencies) around 0.08 indicated little differentiation among streams. Two distance matrices based on allele frequencies (one derived from the total data set and one from a subset that excluded individuals with Florida-subspecific alleles) showed significant correlation (approximate Mantelt-test,P< 0.0001). This indicated that the genetic relationships among all stream populations as a whole were not significantly influenced by individuals with Florida-subspecific alleles. Allele frequencies that were not in Hardy–Weinberg equilibrium (HWE) and heterozygote deficiencies at thesIDHP*andsAAT-B*loci in introgressed populations suggested that the main influence of introgression was localized within individual stream systems. However, the finding of HWE in the population with the highest rate of introgression may have indicated a freely interbreeding mixture in that stream system.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0550:IOTFLB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Circulating levels of the sex steroid hormones testosterone (T) and 11-ketotestosterone in males, and 17β-estradiol (E2) and T in females, were measured at monthly intervals in white perchMorone americanafor 1 year. The egg yolk precursor vitellogenin was also measured in female blood plasma. The gonadal status of individual fish was assessed through histological examination and measurement of gonadosomatic index (GSI), size-frequency distribution of oocytes, sperm index, spermatocrit, and spermiation response. A biphasic pattern of maturation was seen in both sexes. At the onset of vitellogenesis in females, blood plasma levels of E2and T increased moderately in November and then increased again to maximal levels during the spawning season in April and early May. All stages of oocyte development were observed in mature females, indicating that the white perch is a multiple-clutch, group-synchronous spawner. In males, androgen levels and GSI increased early in the reproductive cycle during spermatogenesis in October and November and then increased again to maximum levels during spermiation. Except for the biphasic nature of its reproductive endocrine cycle, the white perch appears to be a typical teleost with respect to gonadal growth and maturation and its hormonal correlates.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0563:ROWPTA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Western mosquitofishGambusia affinisfrom the San Luis Drain (SLD), a major conveyance system for seleniferous agricultural subsurface (tile) drainage water in the San Joaquin Valley, California, experienced lower reproductive success than did mosquitofish from a nearby reference area (Pond 26 at the Volta Wildlife Area, VOLTA) that had no history of receiving tile drainage. At birth, mean survival of SLD fry was 70% in 1984 and 77% in 1985, whereas mean survival of VOLTA fry was greater than 99% in 1984 and 97% in 1985. Measurements of total length (TL) of offspring born to SLD females in 1985 showed that stillborn fry (mean TL, 7.5 mm) were significantly shorter than live fry (mean TL, 9.4 mm). In addition, most stillborn fry were at earlier stages of development (contained prominent yolk sacs or occasionally resembled eyed embryos) than most live fry (yolk sacs were fully resorbed). In comparison, stillborn and live fry born to VOLTA females did not differ significantly in TL (mean for stillborn fry, 7.1 mm; mean for live fry, 7.5 mm), and nearly all fry had resorbed their yolk sacs. Mosquitofish from the SLD contained over 100 μg/g (whole-body concentration in dry weight) of selenium, whereas those from VOLTA averaged 1.5 μg/g. Although experiments are still needed to establish cause and effect, the high incidence of abnormal births of mosquitofish from the SLD is seemingly a response to selenium toxicity.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0578:EOIRBW>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Microhabitat use by brook troutSalvelinus fontinalisand juvenile Atlantic salmonSalmo salarin a small acidic brook was examined in response to the acidification episodes typical of rivers of southwest Nova Scotia in the fall, and to a longitudinal pH gradient related to liming. Several microhabitat variables were measured for age-0 and age-1 and older fish of both species. Some of the measurements were made relative to the fish's focal point (height of the fish above the bottom) and included water depth and focal elevation, focal water velocity, focal water pH and temperature, and bed material grain size. The presence of a small, longitudinal pH gradient (<1 pH unit) along the brook did not alter microhabitat use by brook trout or juvenile Atlantic salmon, either in summer at pH greater than 5.5 or in the fall at pH less than 5.0. Similarly, a major acidification episode in the fall (>1 pH unit; final pH, <4.8) did not cause any major shift in microhabitat use by either species between summer and fall. The use of a particular microhabitat by fish generally reflected its availability, but some preferences in water depth and focal water velocity by age-0 fish ensured that Atlantic salmon and brook trout were effectively segregated at all times.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0588:SOMUBB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We surveyed stream habitats and fish populations at 243 stations among 21 high-elevation trout streams in the Apache–Sitgreaves National Forest and White Mountain Apache Reservation in the White Mountains area, east-central Arizona, from 1986 to 1990. The White Mountains area makes up most of the historic habitat for Apache troutOncorhynchus apache, listed by the U.S. federal government as a threatened species. A generalized linear model relating trout biomass and stream, riparian, and geomorphic habitat variables was developed (R2= 0.68). Among the significant variables in the systematic components of the model, bank damage by ungulates was the only variable solely influenced by land management practices. We attribute the bulk of the bank damage to domestic cattle grazing and conclude that better cattle management is necessary for improvement of trout habitats. Another significant variable, channel width, was partly dictated by geomorphology but was also correlated with bank damage by ungulates. Three significant variables in the model were completely geomorphic (station elevation, channel type, riparian area width) and thus not useful for management purposes. The model coefficient of determination was relatively low in comparison with some other trout-habitat models developed in the western USA. This result may indicate that trouts in our study area are limited less by physical habitat than by climatic events or predation and competition influences.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0599:TBASHR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor