摘要:

Radio telemetry was used to determine the distribution of sockeye salmonOncorhynchus nerkareturning to spawn in the glacial Taku River in 1984 and 1986, and to locate and characterize spawning areas used by this species. During the study, 253 sockeye salmon were tracked as they moved upriver; 204 of these were followed to spawning areas. Only 37% of the 204 fish traveled to areas associated with lakes; the remaining 63% returned to “riverine” areas – river areas without lakes (42% to the Taku River main stem, 17% to the Nakina River, and 4% to other rivers). Sockeye salmon spawning in riverine areas used a variety of habitat types, including main-river channels, side channels, tributary streams, and upland sloughs. Most (55%) of the radio-tagged fish that returned to the Taku River main stem were tracked to side-channel spawning areas. Half of the 471 adult sockeye salmon sampled in main-stem spawning areas had migrated to sea as juveniles before their first winter. This study showed that many sockeye salmon returning to the Taku River do not depend on lakes, and that riverine sockeye salmon make up a major portion of the run in some river systems.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0701:RSBSSI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

During 1984 and 1985, 67 adult Arctic graylingThymallus arcticuswith surgically implanted radio transmitters were released at their summer feeding areas in three river systems of the Arctic National Wildlife Refuge, Alaska. We tracked the fish from aircraft to determine patterns of autumn migration to overwintering locations. During August or September in each area, fish left the small tundra streams where they were tagged and migrated into larger streams. Migration rates peaked at 5–6 km/d about 1 September and averaged 1 km/d. Fish in two river systems moved into adjacent rivers after passage through estuarine waters. Migration distances from spawning or summer feeding areas to overwintering sites were as great as 101 km. Potential overwintering areas determined from transmitter relocations included deep pools, spring-fed areas, and lakes. Management problems associated with these extensive seasonal migrations may include the maintenance of the species migratory circuit in a region that may face future development.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0709:AMAOOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We examined associations between timber harvesting (clear-cutting and associated activities) and structure of assemblages of stream fishes across 89 localities in the Little River drainage, Oklahoma. Timber-harvesting activities were quantified as the percentage of the watershed (upstream from each locality) covered by clear-cuts in each of eight different age-classes. We found significant associations with one or more age-classes of clear-cut for three indices of species diversity, 14 of 29 common fish species, and three of five multivariate axes (principal components) of covariation among species abundances. Further analyses indicated a nonrandom association between life history strategy (r- orK-selection) and whether the abundance of individual species was related positively or negatively to clear-cuts of different ages. The results suggest thatr-selected species (small, short-lived) may respond quickly to clear-cutting perturbations whereasK-selected species (large, long-lived) exhibit a delayed response. The results of this study, together with an earlier survey of faunal changes, suggest that the effects of clear-cutting in the Little River system are limited to temporary changes in local fish assemblage structure.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0716:DEOTHO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The decreased range of native brook troutSalvelinus fontinalisin the Great Smoky Mountains National Park has been attributed to competition with introduced rainbow troutOncorhynchus mykiss. To determine whether brook trout were displaced from preferred sites in the presence of rainbow trout, we made underwater observations of microhabitat use to characterize positions of individual fishes in a section of Palmer Creek, North Carolina, where both species occur. We then reduced rainbow trout numbers by about 80% by electrofishing and repeated our underwater observations on the remaining brook trout to determine whether the species underwent changes in microhabitat use. We found differences in characteristics of focal points selected by the two species. Focal points of age-0 brook trout were similar to those of rainbow trout for distance to overhead cover. After rainbow trout were reduced, age-0 brook trout shifted to positions significantly farther from overhead cover. Brook trout age 1 or older responded to rainbow trout reduction by shifting to positions farther from overhead cover, but to a lesser degree than age-0 fish. No differences in focal-point water velocity were observed between age-0 and older fish of either species before and after rainbow trout were reduced. Shortcomings in our approach to determining the potential role ofcompetition between brook and rainbow trout for preferred stream sites underscore the need for additional research on interactions between these two species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0729:MSBBAR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Ocean surgeonsAcanthurus bahianusand doctorfishA. chirurgusdisplayed no preference between food items containing toxic dinoflagellates associated with ciguatera poisoning and nontoxic food when given a choice for up to 42 consecutive days. Two clones of laboratorycultured dinoflagellatesGambierdiscus toxicusand one clone ofProrocentrum concavumwere used in separate trials.Gambierdiscus toxicusclone SIU-350 was toxic to both fish species after 5–8 d at a daily ration of 2.5 mg of cells per food item. Clinical signs were similar to those previously reported for blueheadsThalassoma bifasciatumfed the same clone, Clinical signs became less pronounced with time, but recurred with equal intensity when the ration was doubled. No difference in food consumption between toxic and nontoxic food types was observed. Fish fedG. toxicusSIU-175, previously shown to be considerably more toxic to miceMussp. and brine shrimpArtemiasp. than toG. toxicusSIU-350, remained asymptomatic at daily rations as high as 7.5 mg of cells per food item. No signs of toxicity were observed in adult brine shrimp that consumed ground muscle and liver tissue from fish fed eitherG. toxicusclone, indicating that ciguatoxicity had not been induced. Results suggest that herbivorous fish may acclimate to, rather than avoid, macroalgae harboring epiphytic toxic dinoflagellates. Attempts to directly relate these findings to nature should be made cautiously because differences in toxic properties between cultured and wild dinoflagellate cells cannot be discounted.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0737:ADNACC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Spotted seatroutCynoscion nebulosus(N= 674) from 12 geographic populations along the Texas and northern Mexico Gulf coasts were surveyed to determine population structure as indicated by the distribution of electrophoretically detectable allelic variants. The percentage of polymorphic loci among 44 putative gene loci averaged 15.5% and ranged from 13.6 to 15.9%. The percentage of heterozygous loci per individual (H) for all loci averaged 1.6% and ranged from 1.2% in East Matagorda Bay to 2.3% in Rio Soto La Marina. A cline existed in the frequency of thesAAT-2*80allele (for aspartate aminotransferase) (0.9–17.1%) and in average individual heterozygosity with respect to degrees north latitude and west longitude, Heterogeneity tests indicated allele counts at thesAAT-2 *locus were distributed heterogeneously among the 12 localities. Subpopulation differentiation was low (FST= 0.012), and quantitative (Nem) and qualitative estimators suggested high gene flow throughout this study area. The correlogram of mean spatial autocorrelation coefficients of allele frequencies indicated response surfaces with short-distance, positive autocorrelation coupled with long-distance negative correlation. This finding conforms well to the spatial patterns expected under an “isolation-by-distance” population model. This study did not provide evidence of independent subpopulations (stocks) of spotted seatrout within Galveston Bay, as previously had been suggested, or among Texas bays, as had been suggested for Florida bays. A westerly directed, nearshore egg and larval transport system moving along the series of closely spaced bay systems may facilitate spotted seatrout gene exchange between Texas bay populations. Enzyme systems coded by rare alleles were identified and could prove useful as genetic markers in a spotted seatrout stocking program.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0746:PSOSSI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

SheepsheadsArchosargus probatocephaluscollected from commercial and recreational catches in Louisiana coastal waters were group-synchronous fractional spawners. Spawning occurred during late February through late April. Gonadosomatic index values corresponded with histological examination of gonads with regard to onset of gonadal development, peak spawning, and cessation of spawning activity; however, specific events could not be identified from gonadosomatic index values alone. Estimates of batch fecundity and spawning frequency were inconclusive in this study because of sample design. Most individuals were mature by age 2. All males over age 3 and all females over age 4 in our study were mature.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0757:RBOSIT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Summer flounderParalichthys dentatuswere collected from intertidal and subtidal polyhaline marsh creeks in the Great Bay–Little Egg Harbor estuarine system in southern New Jersey during 1987–1990 to determine seasonality, duration of creek use by individuals, emigration rate, foraging habits, and daily growth rate of young-of-year fish in those habitats. Four hundred fifty-eight age-0 individuals (mean total length [TL], 238 mm; range, 156–312 mm) were collected from a combination of weir, seine, gill-net, and gig sampling. They were available to the collecting gear from late July through October, peaking numerically in September. Sixty-three (39%) of 162 tagged age-0 summer flounder were recaptured at least once during August–September. The average period of creek use was estimated at 17 d (range, 5–38 d) from release. Decline in percent recaptures suggested an emigration rate of 1.0%/d and 100% emigration within 50 d of release during August–October. Summer flounder appear to undergo tidal movements in and out of the creeks. Average growth rate predicted by length-frequency analysis was 1.7 mm/d, whereas growth rate measured directly from tag recaptures averaged 1.3 mm/d. Summer flounder preyed on creek fauna in order of prey abundance; Atlantic silversidesMenidia menidia, mummichogsFundulus heteroclitus, marsh grass shrimpPalaemonetes vulgaris, and sevenspine bay shrimpCrangon septemspinosacontributed most importantly to their diets. Stomach fullness of fish captured leaving the creeks on ebb tides was significantly greater than that of fish captured entering the creeks on flood tides, suggesting that summer flounder undergo tidal movements to take advantage of high concentrations of prey available in the creeks. These analyses provide compelling evidence that salt-marsh creeks in southern New Jersey are important nursery habitats for young-of-year summer flounder.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0765:FHGATP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Winter flounderPleuronectes americanuscollected in the inner New York Bight were tagged and released to determine generalized movement patterns. Between July 1986 and August 1989, there were 7,346 winter flounder (≥18 cm) tagged at 14 inshore stations in Sandy Hook, Raritan, and Lower bays and the Shrewsbury River and at 22 offshore stations associated with a sewage sludge dumpsite 22 km off the New Jersey coast. Results from 206 tag returns indicated that the Navesink–Shrewsbury river system, part of the Sandy Hook–Raritan estuary, supports a population of winter flounder that returns yearly during the spawning season. Winter flounder exhibited limited seasonal migration and intermixed with other winter flounder from the inner New York Bight, indicating the existence of a dynamic assemblage.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0777:WFMITI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Hatchery-reared kokaneesOncorhynchus nerkamay form discernible “stress” checks on their otoliths when they are stocked into lakes and rivers. We established the reliability of this mark for distinguishing age-0 hatchery fish from wild fish in Lake Pend Oreille, Idaho. Hatchery fish marked with dietary oxytetracycline (OTC) were recaptured 1–3 months after they had been stocked in the lake. All specimens with OTC marks on their bony structures also had a stress check. We also validated daily otolith increments for age-0 kokanees by comparing increment counts external to the stress check with known days between release and recapture of hatchery fish. Then, counts of daily increments allowed us to correctly identify fish from several co-occurring release groups that had been stocked at different times in the same season. Such discrimination will enhance evaluations of alternative stocking strategies. Because some otolith growth increment counts varied slightly from days at large, and because fish released in cold, food-poor, or otherwise unfavorable sites apparently did not resume otolith growth immediately, we recommend that groups of kokanee be released at least 7 d apart if they are to be subsequently identified by otolith analysis.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0785:UODGIO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor