摘要:

Abundanes of tilefishLopholatilus chamaeleonticepsoff South Carolina and Georgia are lower than previously estimated. Mean density of tilefish burrows, determined by counts from side-scan sonar records, decreased from 258 burrows/km2in 1986 to 13 burrows/km2in 1987 in overlapping transect segments at one site. A bimodal depth distribution of burrows was believed to be due to the presence of burrows of blueline tilefishCaulolatilus micropsin water shallower than 160 m, especially at the southernmost site, andL. chamaeleonticepsburrows typically in greater depths. The mean catch ofL. chamaeleonticepsper 100 hooks was greatest within the water temperature interval of 13.0–14.4°C (5.4 fish/ 100 hooks) and within the depth interval of 194–203 m (5.3 fish/100 hooks). Within comparable areas and depths, a general trend in decreasingL. chamaeleonticepslengths and catch per unit effort from research fishing was supported by similar trends in data from South Carolina commercial landings between 1977 and 1989. Recent landings indicated thatL. chamaeleonticepsis still being harvested and mean length has continued to decrease. Presently, the fishery should be managed by reducing the fishing effort.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0165:TITDAR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

I examined the characteristics and dynamics of a population of wild steelheadOncorhynchus mykissin the Little Manistee River, an extremely stable-flow, low-gradient (sandy) tributary of Lake Michigan. I monitored autumn pan populations by electrofishing (1981–1983), and I monitored spring emigrant populations at a weir near the river mouth (1982–1984) and both autumn- and spring-returning adults at this weir (1979–1987). Relative to other Great Lakes populations, steelhead in the Little Manistee River had several notable characteristics that are probably linked to abundant groundwater and stable flows: (1) high abundances of age-1 parr, smolts, and adults, (2) constant autumn age-1 parr densities, (3) few emigrant parr, (4) fast growth when in the stream environment, and (5) relatively late age at maturity (after 3 years in the lake). An excessive sand bed load occurs in the low-gradient sections of the river, limiting gravel spawning areas to higher-gradient sections. This limited spawning area likely caused the relatively low abundance of age-0 parr, and may also be a factor in late age at maturity. Abundance and age structure of returning adults varied because of (1) variable survival during the presmolt winter (13–90%), (2) variable survival from smolt to maiden adult (6–29% for spring-run maiden spawners), and (3) variable survival to repeat spawn (3–58%). Most adults returning from a marked smolt cohort originated in the Little Manistee River (mean ± 95% confidence limit, 71 ± 28%). Management of such populations needs to focus on protecting and enhancing the stream environment, and on managing sport harvest. Modeling population dynamics will require development of long-term data sets.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0179:PBOSIA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The colonization of Illinois streams by fishes was measured during late spring and early summer in 18 experimentally depopulated reaches that ranged from 46 to 113 m in length. Rates of colonization in terms of total fish numbers, number of species, individual species, and community structures were measured over time intervals ranging from 0.5 to 140 h. Both the proportion of original fish abundance (all species) and the proportion of original community structure (measured by a proportional similarity index) increased with time. Linear colonization models indicated that 0.70 of the maximum proportional similarity index would be reached in 60–140 h (90% confidence limits of the model) and that 0.90 of the original fish abundance would be reached in 100–270 h. The results of this and previous studies indicate that in drainages dominated by surface runoff, disturbed fish communities in short stream reaches can quickly return to their original structures and abundances without any aid, provided that fish have unrestricted access to the reaches and that the environment returns to its original state.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0199:CROFIE>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Spawning and nursery habitats of largemouth bassMicropterus salmoidesin the freshwater portion of the Hudson River estuary were identified and characterized. The shoreline from Troy to Peekskill, New York, was classified by habitat (exposed shoreline, shallow shoreline, creek mouths, coves, and bays), and 15 adult males, radio-tagged in March, were tracked to nesting sites. Fish moved 1.6–64 km and spawned in areas protected from wind and wave action or in areas where tidal action was mitigated. Bays and coves were the habitats selected by most nesting radio-tagged bass. Nests of 114 untagged largemouth bass were visually located; 44% of these nests were in bays, 37% in creek mouths, 18% in coves, and only 1% along exposed shoreline. Habitat types selected by nesting largemouth bass amounted to less than 25% of the total shoreline habitat available. Water temperatures over the nests when the nests were first discovered ranged from 16.7 to 20.5°C, and depth of the nests at low tide ranged from 0.15 to 1.10 m. One nest was dewatered at low tide. Electrofishing catch rates for age-0 largemouth bass indicated that areas selected for nesting were also the primary nursery habitats. Suitable spawning and nursery habitats for largemouth bass in the Hudson River are limited and should be safeguarded to ensure the health of the local largemouth bass sport fishery.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0208:SANHOL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Spawning and rearing habitats used by white sturgeonsAcipenser transmontanuswere described from water temperature, depth, and velocity measurements and substrate types present at sites where eggs, larvae, young-of-the-year, and juveniles (ages 1–7) were collected. Spawning and egg incubation occurred in the swiftest water available (mean water column velocity, 0.8–2.8 m/s), which was within 8 km downstream from each of the four main-stem Columbia River dams in our study area. Substrates where spawning occurred were mainly cobble, boulder, and bedrock. Yolk-sac larvae were transported by the river currents from spawning areas into deeper areas with lower water velocities and finer substrates. Young-of-the-year white sturgeons were found at depths of 9–57 m, at mean water column velocities of 0.6 m/s and less, and over substrates of hard clay, mud and silt, sand, gravel, and cobble. Juvenile fish were found at depths of 2–58 m, at mean water column velocities of 1.2 m/s and less, and over substrates of hard clay, mud and silt, sand, gravel, cobble, boulder, and bedrock.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0217:SARHUB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Available summer habitat for northern pikeEsox luciusin southern Ohio impoundments is restricted by warm epilimnetic temperatures and anoxic bottom waters. We used temperature-sensitive radio transmitters to determine locations of adult northern pike in two impoundments, and we related seasonal growth of other tagged fish to availability of suitable habitat. We implanted transmitters in eight fish in one lake and nine fish in the other; fish locations were monitored from April to October. Condition factors were highest in spring and lowest in late summer. Individually tagged fish lost weight during summer. At the onset of summer thermal stratification, fish moved from inshore to offshore locations that were frequently associated with macrophytes or bottom structures such as submerged stream channels. When lake surface temperatures exceeded 25°C, fish were found in the coolest available water with dissolved oxygen concentrations of at least 3.0 mg/L, and they were restricted to this stratum for 2–3 months. Although northern pike lost weight during the period of habitat constriction, their annual growth exceeded the average for the species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0228:RSHAGO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

I produced triploid white crappiesPomoxis annularisin the laboratory by subjecting stripped eggs to 5°C for 90 min. This treatment produced triploids on three out of seven attempts, yielding 92%, 93%, and 100% triploids. I compared several hematological characteristics of adult triploid and diploid white crappies. Triploids had significantly lower concentrations of circulating red blood cells and hemoglobin than diploids but their red blood cells had significantly greater volumes and hemoglobin contents. Diploids had significantly higher gonadosomatic indices. Diploids and triploids did not differ significantly in heart weight as a percentage of body weight or in standard metabolic rate, active metabolic rate, or critical swimming speeds. Despite the hematological differences, nonreproductive triploid white crappie adults appear to be as fit for survival as normal diploid fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0237:COTADW>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Oxygen uptake by larval striped bassMorone saxatilis12–22 d posthatch was converted to joules in order to estimate daily food requirements. I measured resting metabolism (in darkness), routine metabolism (in light without food), and active metabolism (with food) in contrasting treatments (dark-light, nonfeeding-feeding). Metabolism differed significantly between nonfeeding and feeding larvae but not between nonfeeding larvae in darkness and light. Ratios of active to resting weight-specific metabolism were 1.8 and 1.9 for younger and older larvae, respectively, and were below ratios commonly cited in the literature. Larvae needed an average of 2.06 J/d to grow and support metabolism, an equivalent of 57Artemianauplii or 73 copepod nauplii. Oxygen uptake and ingestion were slightly higher than previously published values for striped bass, possibly due to larger respirometers and faster gut evacuation times. The proportion of ingested energy metabolized was relatively high (35–50%), suggesting that striped bass larvae allocate considerable energy to activity.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0244:EFROSB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In our 2-year laboratory study of hatchery-reared adult lake troutSalvelinus namaycushof the Seneca Lake, Marquette (Lake Superior Lean), and Jenny Lake strains, we compared gamete ripening times and changes in plasma concentrations of seven hormones. If interstrain differences in these traits were found, such differences might help explain the apparent failure of stocked fish of these strains to develop large, naturally reproducing populations in the Great Lakes. The complex temporal changes in plasma hormone levels that occur during sexual maturation in lake trout have not been previously described. We detected little evidence of temporal isolation that would prevent interbreeding among the three strains. Strain had no effect on ovulation date (OD) in either year. Strain did not affect spermiation onset date (SOD) in year 1 but did in year 2, when the mean SOD of Jenny Lake males was earlier than that of Seneca Lake males but not different from that of Marquette males. Hormonal data were normalized around ODs for individual females and SODs for individual males. In females, estradiol-17β (E2) was highest 8 weeks before the OD; the highest testosterone (T) level occurred 6 weeks before the OD, and the next highest level occurred simultaneously with the highest level of 11-ketotestosterone (11-KT) 2 weeks before the OD. Plasma levels of 17∝-hydroxy-20β-dihydroprogesterone (DHP) peaked 1 week before the OD, then abruptly declined immediately after. Cortisol (F), triiodothyronine (T3), and thyroxine (T4) were highly variable, but F was the only hormone that showed no trend with week in either year. In males, plasma E2 levels were highest 3 weeks before the SOD, highest levels of T and of 11-KT occurred simultaneously 2 weeks after the SOD, and DHP peaked 5 weeks after the SOD and 3 weeks after the highest levels of T and 11-KT. As in females, plasma levels of F, T3, and T4were highly variable, and F was the only hormone that showed no trend with week in either year. Strain had no effect on any hormones in females and only on T and F in males. The lack of pronounced interstrain differences in gamete ripening dates and reproductive endocrinology and the similarity of the temporal patterns and relative concentrations of hormones to those reported for other salmonids suggest nothing unusual or dysfunctional about these reproductive traits that would impede lake trout rehabilitation in the Great Lakes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0252:GRAHCI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We evaluated, for brook troutSalvelinus fontinalisin three streams that undergo episodic acidification during critical periods of embryo development, survival of embryos from egg deposition to preemergence in natural redds and survival of sac fry in toxicity tests done in situ. Twenty-five natural redds were used for comparisons among streams. Median survival to preemergence (range, 16–68%) was different (P≤ 0.05) among streams and was inversely related to stream concentration of inorganic monomeric Al. Survival to preemergence was not related to intragravel dissolved oxygen concentration, gravel quality, or depth or velocity of stream water at redd sites. Median survival of sac fry exposed to stream water for 39 d was different among streams (range, 51–95%) and was inversely related to stream concentration of inorganic monomeric Al. Episodic acidification could lead to declines in populations of brook trout by causing decreased survival of early life stages.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0268:SOBTEI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor