摘要:

Trends in U.S. domestic commercial seafood landings during 1880–1995 coincide with changes in factors known to determine consumer demand for seafood and with technological innovations in transportation, power, food processing, and electronics that permeated the fishing industry. Although controversial, the repeated failures of centralized command-and-control management by the public sector to prevent overfishing and the resultant economic waste in the seafood industry draw attention to alternative property institutions that could make harvesters accommodate macroeconomic change in ways that sustain yield.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0001:IOACOM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

To evaluate effects of habitat modification at different spatial scales, we assessed species richness and tolerance of fish assemblages in littoral zones of 17 Wisconsin lakes with extensive residential and recreational development, and compared fish associations among site-specific and lakewide conditions. Samples consisted of combined DC electrofishing and seining. Stations were randomly selected within strata defined by type of shoreline erosion control structure, including retaining walls, rock riprap, and no structure. Habitat characteristics differed among the site types. Species richness at the site level was greatest in complex habitat (riprap) regardless of fish assemblage structure. However, more effort was required to achieve complete sampling of fish species present in sites without erosion control structures. This result may be related to homogeneity of habitat among sites altered by manmade structures. We used an analysis of covariance (ANCOVA) to compare site level habitat effects with basin scale impacts as indexed by total phosphorus, which is affected by land use in the riparian zone and surrounding watershed. Although species richness is positively correlated with local habitat complexity across the range of lakes sampled, assemblage structure, assessed as proportion of intolerant or tolerant species, shifted in response to cumulative effects. Habitat management programs, such as shore land zoning and permitting, should consider the cumulative effects of small habitat modifications in addition to local effects.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0018:CEOISH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Florida commercial shark landings rose from 287,531 lb in 1980 to 7.3 million pounds in 1990, an increase of more than 2,400%. Two reasons for this increase in landings were the growing public acceptance of shark meat as a seafood product and the subsequent increase in prices in the Asian market for shark fins. Landings then declined in 1991 and 1992. Commercial and recreational landings data and responses to mail surveys have supplied important information regarding Florida's shark fisheries. The sandbar shark Carcharhinus plumbeus and the blacktip shark C. limbatus accounted for 84% of the sharks landed in the commercial fishery in 1989. Commercially fished sharks are captured primarily by longline gear. After 1986, sharks were targeted much more frequently in the commercial fishery. Although catch per unit of effort steadily increased, landings and effort decreased during the 2 years before the implementation of regulations. Fewer sharks were landed in the recreational fisheries than in the commercial fisheries after 1986. Recreational landings declined considerably from 1990 to 1992, and the species of sharks landed differed from those landed in the commercial fishery. During the 1930s and 1940s, sharks were easily overexploited, so the recreational and commercial fisheries' ability to sustain elevated harvest levels is currently very much in question. Shark life history data explains this potential vulnerability to overfishing. Resource managers have used detailed fishery data and life history information to develop regulations that will help reduce the overexploitation of shark species in waters adjacent to Florida.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0028:TITCAR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Bycatch reduction is a major issue in many U.S. fisheries, and workers in the U.S. Gulf of Mexico menhaden industry have used bycatch reduction devices since the 1950s. Currently industry workers employ a hose cage and a large fish excluder, usually in combination, to reduce the retention of large bycatch species (defined here as any vertebrate species 1.0 m or greater in total length). In this paper, we examine the effectiveness of these devices to reduce large bycatch and recommend possible modifications of the devices to further reduce the bycatch. A principal component analysis was conducted to assess possible groupings of bycatch reduction devices. The analysis suggested that a hose cage with a larger area and smaller openings would be effective at mitigating the retention of large bycatch.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0042:CAEOBR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Passage and transit time of adult upstream-migrant American shad Alosa sapidissima and blueback herring A. aestivalis were investigated in standard Denil and Alaska steeppass fishways with variable slope and headpond under semicontrolled conditions. Percent of American shad passed per unit time (percent passage) increased with temperature, while time required to ascend from the fishway entrance to the exit (transit time) decreased with increasing temperature for both species. Increasing fishway slope decreased percent passage of American shad, regardless of fishway type. Higher fishway slope decreased percent passage of blueback herring in the steeppass fishway only. Low headpond enhanced percent passage of American shad in the Denil fishway, but decreased percent passage of American shad in the steeppass fishway. Headpond level had no effect on percent passage of blueback herring in either fishway. Because headpond level in the steeppass fishway affected percent passage of American shad but not the smaller blueback herring, the relatively small cross-sectional area of the steeppass fishway operated at low headpond may inhibit passage of larger species such as American shad. Transit time of American shad decreased with both increasing slope and high headpond, and American shad increased through-water swimming speed under these conditions. American shad appeared to regulate their swimming speed through Denil-type fishways below maximal values. Blueback herring ascended the fishways at speeds comparable to those of American shad. Shorter transit times were not associated with increased percent passage. Turbulence and air entrainment may influence percent passage of American shad more than longitudinal water velocity.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0051:EOSAHO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Largemouth bass Micropterus salmoides populations declined in Kentucky and Barkley lakes following a severe drought during Dec 1984–Oct 1988 and below normal rainfall in three of four years during 1989–1992. Regression models developed for both reservoirs indicated that recruitment of largemouth bass to age 1 was positively related to the electrofishing catch per unit effort (CPUE) of large age-0 bass and negatively related to annual rainfall amounts and the CPUE of all sizes of age-0 largemouth bass. These variables explained 73% of the variation in CPUE of age-1 bass at Barkley Lake and 60% at Kentucky Lake. We also developed regression models to estimate the recruitment of largemouth bass to the fishery at age 5 and older. Recruitment to the fishery at Kentucky Lake was positively related to the CPUE of age-1 bass and negatively related to reservoir discharge. This model explained 52% of the variation in recruitment to age 5 and older largemouth bass. Recruitment to age 5 and older fish at Barkley Lake was positively related to the CPUE of age-1 bass and rainfall and negatively related to reservoir discharge. The model developed at Barkley Lake explained 82% of the variation in recruitment of largemouth bass to the fishery. The models predicted that the largemouth bass fisheries at both reservoirs would decline through 2001 under the current angling regulations, which include a 356-mm minimum length limit and one fish less than 356-mm total length allowed in the angler's creel. We used these models, in consultation with the public, to change length limits to a 381-mm minimum length limit in an attempt to moderate the expected declines in older fish.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0059:MOLBAK>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Factors affecting recruitment of largemouth bass have frequently been evaluated, but few studies have assessed recruitment potential among a range for reservoirs of varying trophic states. We examined densities of larval threadfin shad Dorosoma petenense and gizzard shad D. cepedianum from Mar to Jul from nine Alabama impoundments. Using shoreline rotenone sampling and daily otolith rings, we estimated density, age, and growth of age-0 largemouth bass Micropterus salmoides in late Jun–Jul. Density and growth of larval gizzard shad, larval threadfin shad, and age-0 largemouth bass increased with chlorophyll a across impoundments. Duration of occurrence for larval gizzard shad and threadfin shad was positively related to chlorophyll a. Eutrophic reservoirs contained larval shad that were 40% or less of mean age-0 largemouth bass total length (i.e., the size at which they would probably be vulnerable to predation) in late Jun–Jul, whereas larval shad were generally not collected in late Jun or Jul in oligo–mesotrophic impoundments. Thus, piscivory on age-0 shad by age-0 largemouth bass was more likely to occur in eutrophic than in oligo–mesotrophic reservoirs. Eutrophic impoundments have high chlorophyll-a values and high larval threadfin shad and gizzard shad densities, and they may provide for greater recruitment of largemouth bass than oligo–mesotrophic impoundments.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0067:ROLBIA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Age-0 largemouth bass Micropterus salmoides and spotted bass M. punctulatus were collected from Normandy Reservoir, Tennessee, 1992–1996, to evaluate effects of reservoir hydrology and hatching of shad Dorosoma spp. on hatching and first-year growth and survival of these two species. Fish were collected in cove rotenone samples in early Aug and electrofishing samples biweekly throughout the summer; hatch dates and age-specific growth for both species were determined from cove samples with sagittal otoliths. Hatching of both species ranged from early April to early Jun. Initiation of largemouth bass spawning, but not spotted bass spawning, was positively related to the first day water levels achieved full pool. Mean hatch dates of both species were positively related to the first day of full pool. Timing of spawning for both species was not related to water temperature. Largemouth bass exhibited bimodal length-frequency distributions by midsummer in two wet years and length frequencies were unimodal in dry years; spotted bass always formed unimodal length-frequency distributions. When largemouth bass exhibited bimodal length distributions, earlier hatched fish grew faster than later hatched fish. Spotted bass grew at similar rates, regardless of hatch date, every year except during 1992 when later hatched fish grew faster than earlier hatched fish. Weekly survival of largemouth bass in their first summer was positively related to reservoir water level. First-year growth of both species was not directly affected by the timing of threadfin shad D. petenense or gizzard shad D. cepedianum hatching.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0078:EORHOR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Largemouth bass Micropterus salmoides were collected from Lake Lillinonah and Pickerel Lake, Connecticut, during three sampling periods in 1996: spring (May 14–15); summer (Jul 22–30); and fall (Oct 10–17). Total mercury concentrations ranged from 0.106 to 2.293 μg/g in Lake Lillinonah and from 0.456 to 1.762 μg/g in Pickerel Lake. In both lakes, there was a significant positive relationship between total mercury concentration and length and age during each season. Mean mercury concentrations adjusted for length were significantly different among seasons in Pickerel Lake (P = 0.0002) and Lake Lillinonah (P = 0.0006) and were 26–43% higher during spring than summer and fall in both lakes. Mean mercury concentrations adjusted for age were significantly different among seasons in Lake Lillinonah (P = 0.02) but not in Pickerel Lake (P = 0.06). In Lake Lillinonah, mean mercury concentrations adjusted for age were significantly higher during spring than during fall (P < 0.017). These results suggest that researchers may want to assess mercury concentrations in largemouth bass during standardized sampling periods so that data can be more accurately compared among water bodies and tracked over time.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0089:SVICOM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Population characteristics of bluegill Lepomis macrochirus and associated species were studied intensively to determine why many large bluegills were present at two Michigan lakes—Dead Lake and Blueberry Pond—in which macrophytes covered 41–83% of the surface. Both lakes contained unusually high proportions and densities of bluegills greater than 203 mm in total length due to high survival of adults, low fishing mortality, a favorable growth pattern, and low recruitment to age 2 or 3. Growth was rapid from 75 to 200 mm, then growth slowed and condition deteriorated among older fish. Rapid growth was stimulated by consistently low recruitment and consumption of limnetic Daphnia spp. and littoral benthos for food. Low recruitment was partially due to predation; a diet study at one lake estimated 303,300 juvenile bluegills per year were consumed by piscivores, mostly largemouth bass Micropterus salmoides. Each lake contained dense populations of slow-growing piscivores, but these fish constituted less than 20% of the total fish biomass. Observations indicated that few adult bluegills attempted to spawn in Blueberry Pond, and this lack of spawning was probably more important than predation in controlling bluegill abundance. A supplemental pond study demonstrated that young and old adults of varying condition had normal reproductive potential. The triggering of spawning behavior may be linked to adult density, and perhaps adult growth, by behavioral or bioenergetic mechanisms. The implication for fisheries management is that weedy lakes need not be dominated by small, stunted bluegills but are capable of producing large bluegills if fishing harvest is restricted and a favorable food chain is present.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1999)019<0097:DOQBPI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor