摘要:

Harvest restrictions on striped bassMorone saxatilisfisheries in Atlantic coastal states were relaxed in 1990, but consistent, coastwide regulations of the harvest have been difficult to implement because of the mixed-stock nature of the fisheries and the recognized contamination of Hudson River fish by polychlorinated biphenyls (PCBs). We examined PCB concentrations and stock of origin of coastal striped bass to better understand the effects of these two factors on the composition of the harvest. The probability of observing differences in PCB concentration among fish from the Hudson River stock and the “southern” group (Chesapeake Bay and Roanoke River stocks combined) was investigated with the logit model (a linear model for analysis of categorical data). Although total PCB concentrations were highly variable among fish from the two groups, striped bass classified as Hudson River stock had a significantly greater probability of having PCB concentrations equal to or greater than 2.00 mg/kg than did fish belonging to the southern group for all age- and size-classes examined. There was a significantly greater probability of observing total PCB concentrations equal to or exceeding 2.00 mg/kg in fish that were 5, 6, and 7 or more years old, and this probability increased linearly with age, We observed similar results when we examined the effect of size on total PCB concentration. The minimum-size limit estimated to permit escapement of fish to sustain stock production is 610 mm total length. Unless total PCB concentrations decrease in striped bass, it is likely that many harvestable fish will have concentrations that exceed the tolerance limit set by the U.S. Food and Drug Administration.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0541:SBSACO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We sampled ichthyoplankton, zooplankton, and juvenile fish during May, August, and November 1988 from 15 excavated floodplain ponds along the Mississippi River. In May, densities of larval shadDorosomaspp. ranged from 1.1 to 87.8/m3and densities of larval sunfishLepomisspp. ranged from 0.3 to 19.3/m3among ponds. Ponds with long (>1,800 m), sinuous shorelines, high volumes (>55,000 m3), and variable depth had high ichthyoplankton densities (>50/m3); smaller, low-volume ponds frequently had low ichthyoplankton densities (<10/m3). Ponds that sustained high densities of larval sunfish during May had high numbers of young-ofthe-year sunfish in August and November, which suggests that ponds with high ichthyoplankton densities ultimately contributed more fish to river populations. Pond morphometry probably did not affect food availability, because zooplankton densities were not correlated with ichthyoplankton densities and larval threadfin shadD. petenensegrew faster in ponds with high shad densities. Morphometry may have regulated access of spawning adults to ponds or affected larval fish growth and survival in ponds. Future excavations should adhere to guidelines used by the U.S. Army Corps of Engineers to ensure that ponds function as viable fish nursery areas.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0552:RBMOEF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Summer abundance of young coho salmonOncorhynchus kisutch, steelheadO. mykiss, and Dolly VardenSalvelinus malmawas assessed in small streams on Prince of Wales Island, Alaska, in an attempt to measure the response of these fish to various types of cover alterations. The standing crop of subyearlings decreased during summer, but none of the decrease could be attributed to the changes in cover we made. Subyearling coho salmon (about 75% of the fish present) did not respond either to the removal of natural riparian vegetation or to the addition of simulated riparian canopy, large boulders, woody debris, or simulated undercut banks. Localized movements within the streams were sufficient to provide relatively rapid recolonization of the experimental habitat units. The forms of cover we evaluated were relatively unimportant in regulating abundance of young coho salmon in small streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0562:ROCATT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We used both microhabitat and macrohabitat analyses to better assess habitat requirements of young Colorado River cutthroat troutOncorhynchus clarki pleuriticus. Microhabitat analyses revealed that among a range of stream types, young cutthroat trout consistently preferred slow water (<0.06 m/s) and depths over 3 cm. Suitable habitat of this type was provided by different types of pool habitat within the geomorphically diverse study streams. Macrohabitat analysis indicated that the density of young cutthroat trout was positively correlated with the abundance of spawning gravel and negatively correlated with stream depth (adjustedR2= 0.67). This relationship helped explain the absence of young cutthroat trout from some stream reaches that had suitable microhabitat but that often lacked suitable spawning habitat. The two types of habitat analysis provided complementary information concerning the habitat requirements of young Colorado River cutthroat trout in the study streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0571:AHROYC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We sampled redds of brown troutSalmo truttain a mountain stream to describe egg location and substrate composition after spawning and during egg incubation. A single-probe freeze-coring device was used to sample egg depth and substrate composition. We found eggs throughout redds but most often in the front half of the tailspill (the substrate mound that accumulates as the redd is excavated progressively upstream). Eggs were buried between 2 and 23 cm below the substrate surface but were most frequently 9–12 cm deep. Spawning fish cleaned substrate particles less than 6.3 mm in diameter from egg pockets, yet the percentage of particles smaller than 1.7 mm in egg pockets was correlated with that outside redds. Egg pockets contained particles larger than 50 mm more often than did any other location, indicating that particles of this size were used as egg pocket centrums. The percentage of 1.7-mm and smaller particles in egg pockets was higher in winter than in fall. We conclude that (1) spawning brown trout 20–40 cm in total length substantially alter the substrate in egg pockets; (2) the amount of fine sediment in egg pockets is positively correlated with that in the adjacent streambed; and (3) fines accumulate in egg pockets during the incubation period.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0582:DOBTRI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We used 2 years' diel food weight data from stomachs of Lake Erie yellow perchPerca flavescensto make Elliott-Persson (E–P) estimates of daily ration and to construct consumption response surface (CRS) regression models. The CRS models provided relatively accurate, low-cost estimates of daily ration from only one to four fish collections – compared with nine for the E–P procedure. Besides reducing daily sampling effort, CRS models allowed flexibility in fish collection times, thus alleviating the need for 24-h associations with sampling sites. Independent variables for CRS models included the food weight in fish stomachs from a particular collection (adjusted for water temperature) and the time of day when a fish collection was made. Accuracy of CRS model estimates of yellow perch daily ration relative to E–P estimates was evaluated with a jackknife-like procedure. Effectiveness of CRS models arose from significant relationships that existed between food weights in yellow perch stomachs throughout certain periods of the day and average food weight in stomachs over 24 h. Similar relationships, and hence low-cost estimation potential, are expected for other fish species with regular diel feeding activity. Because CRS models reduce time requirements in the field, they should allow more detailed coverage of important spatial and temporal variability in multiday food consumption studies for fishes. The CRS models also showed spatial robustness and a desirable capacity to estimate daily rations in years beyond those for which the models were developed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0589:LFEOYP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Threadfin shadDorosoma petenenseand blueback herringAlosa aestivaliswere introduced into Jocassee Reservoir, South Carolina, in the early 1970s as prey for large piscivores. To assess the potential for trophic competition between these clupeids, we examined their diets and the extent of diet overlap in May, August, and December 1982 and February 1983. The diet of blueback herring consisted mainly of large species of cladocerans and copepods supplemented in August withChaoborus punctipennisand young fish. Mean length of the organisms eaten by blueback herring was 1.4 mm. Threadfin shad fed on smaller species of cladocerans and copepods, as well as on rotifers and copepod nauplii. The mean length of the organisms eaten by threadfin shad was 0.4 mm, which differed significantly from the mean length of the zooplankton population in Jocassee Reservoir (0.6 mm). Phytoplankton contributed 24 and 32% of the stomach contents of threadfin shad in August and December.Bosmina longirostriswas important in the diet of both species, although blueback herring showed negative selection for it. Diet overlap between the two clupeids was low on all four dates. Although we found no evidence of trophic competition between the two species in Jocassee Reservoir, we do not recommend stocking them together, because both species are voracious planktivores and blueback herring are piscivorous.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0605:FOBHAT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Lipid and fatty acid contents of fillets (with skin) of Atlantic croakersMicropogonias undulatus, striped mulletMugil cephalus, and summer flounderParalichthys dentatuswere determined for three harvest dates over a 1-year period. In striped mullet and Atlantic croakers, total lipid increased significantly (P≤ 0.05) in late summer (from 21.72 to 31.78% and 12.68 to 31.94% of dry weight, respectively). No significant change in total lipid content was noted in the leaner summer flounder (9.38–9.87%). However, polyunsaturated fatty acid (PUFA) content of fillets of summer flounder varied significantly (P≤ 0.05), ranging from low levels in June and August (6.24 and 3.33% of dry weight, respectively) to much higher levels (17.32%) in January. The difference in PUFA content of fillets was due mainly to a significant increase in docosahexaenoic acid (22: 6n3). The PUFA content of Atlantic croakers (22:6n3) also increased significantly (from 3.19 to 6.16%) from August to January, but the PUFA content of striped mullet did not change significantly. These results indicate that generalizations cannot easily be made concerning the lipid and fatty acid composition offish. We speculate that for some species (e.g., Atlantic croaker and striped mullet), high food availability linked with preparation for spawning is a primary determinant of lipid content, but for other fish (e.g., summer flounder), changes of PUFA content in response to temperature change are more important.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0614:VILAFA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Past population estimates of adult walleyesStizostedion vitreumcan be used to set harvest quotas, provided that temporal variability in abundance of adult walleyes is accounted for. We used a long-term data set from Escanaba Lake, Wisconsin, to evaluate the accuracy of past population estimates for setting current-year quotas for adult walleyes. The results from Escanaba Lake were corroborated by comparison with other lakes where adult walleye abundance was estimated in more than 1 year. The accuracy of estimates of adult walleye abundance declined over time from the year the estimate was obtained to the year it was used to set a harvest quota. We derived safety factors for application to past estimates of population size; these factors limit the occurrence of an exploitation rate exceeding the maximum sustainable rate (35%) to approximately 1 in 40. These safety factors declined from 35% for 1-year-old estimates to less than 20% for 10-year-old estimates.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0620:DOSFFS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The physiological effects of catch-and-release fishing on largemouth bassMicropterus salmoidesfrom Lake Powell and Mantua Reservoir, Utah, were evaluated, and an estimate of the time needed for recovery from hooking stress was obtained. Fatigue in Lake Powell fish, as indicated by elevated blood lactate, was directly proportional to hooking time (1–5 min) and water temperature, but recovery from the hyperlacticemia was relatively rapid (about 24 h). Hyperglycemia, an indicator of stress hormone production, did not occur in largemouth bass hooked and played for 1–5 min in the coldest water (11–13°C), was moderate in fish hooked and played at l6–20°C, and was severe in fish played for 5 min at 28–30°C. Fish held for recovery in live cages suffered further hyperglycemia, presumably because of the stress of confinement. Ionoregulation, as indicated by relatively stable plasma chloride values, was not immediately affected in largemouth bass caught at water temperatures of 11–13°C or 28–30°C, but an unusual hyperchloremia developed in fish hooked and played at 16–20°C. During recovery, the expected progressive hypochloremia developed. Plasma osmolality was somewhat affected by hooking at all water temperatures tested, but recovery was almost complete within about 8 h. Mantua Reservoir fish were hooked and played only at water temperatures of 23–26°C. The hyperlacticemia and hyperglycemia that occurred were generally more severe than in the Lake Powell fish hooked and played at either 16–20°C or 28–30°C. However, effects on plasma chloride and osmolality were similar to those occurring in Lake Powell fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0629:PROLBT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor