摘要:

Juvenile largemouth bassMicropterus salmoideswere collected by electrofishing during October through March 1992–1994 from coves (≤25 ha) covered with aquatic macrophytes over 1–65% of their area. Mean total length of juvenile largemouth bass was highest in coves with the least vegetated cover, but increase in mean length between October and March was highest in coves having near 20% vegetation coverage. Catch per unit effort decreased between October and March; decreases were least at vegetation coverages near 10–20%, highest at coverages of 5% or less, and intermediate at coverages of 30–65%. By March, these disparate decreases contributed to the formation of a dome-like relationship between vegetation coverage and catch per unit effort. Consumption of fish foods was highest when vegetation coverage was low, but decreased asymptotically as coverage increased; consumption of invertebrate foods increased at low coverage, peaked near 20–30% coverage, and decreased at higher coverage. We suggest that greater length increases and greater abundance at 10–25% vegetation coverage were stimulated by a favorable blend of food availability and cover. Our results support reports that maximum recruitment of largemouth bass occurs at intermediate levels of vegetation coverage, and we further suggest that such increased production is reinforced during winter, when survival. invertebrate consumption, and length increases are highest at intermediate levels of vegetation coverage.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0601:RBVCAA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Access point angler surveys are conducted at numerous ports on the Great Lakes and on inland waters each year in Michigan to estimate angling effort and catch. Estimated catch is the product of estimated angler-hours and catch rate. Catch rate has been determined by averaging angler party catch per hour by species, angling mode, and time period. Effects of bias on accuracy and precision of catch per hour estimates were measured by using Monte Carlo sampling techniques on 132 completed trip interview data sets from Michigan access point angler surveys. Estimated mean catch rate by angler party was significantly greater (P∝≤ 0.05) than population catch rates in 82 data sets and significantly less in 49 others. Due to biases associated with trip length and angler party size, the sample confidence limits were incorrectly represented in 123 of 132 data sets. I concluded that averaging angler party catch rates of completed-trip interviews is inappropriate for Michigan access point angler surveys. Calculating catch rate by dividing total catch by total hours from completed-trip angler interviews eliminates the bias.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0611:EOCREF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Management of angler harvest of walleyesStizostedion vitreumassumes that angling catch rates can be regulated by fish densities. Data on walleye densities in northern Wisconsin lakes obtained between 1990 and 1993 were used to develop a predictive model for walleye angling catch rates. Data collected in 1993–1994 were used to validate these models. Total numbers of walleye per acre were estimated from mark-recapture experiments conducted during April and May of each year. Creel surveys were conducted starting on the first Saturday in May and ending on 1 March of the following year for waters where population estimates were made. Linear regression indicated a high correlation between walleye densities and yearly walleye catch rates (r= 0.92,P< 0.05). Using the linear equation generated from this analysis, we predicted yearly walleye catch rates from walleye population estimates in 11 lakes for 1993–1994. All 11 angler catch rates were within the 95% prediction intervals. When data from 1993–1994 were added to the linear predictive model for all lakes, there was no change in the slope. We conclude that total walleye densities are a good predictor of angling catch rates.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0621:POACRB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We investigated the effects of prey availability on relative weights (Wr; the ratio of fish weight to the weight of a standard fish of the same length) in populations of walleyeStizostedion vitreumfrom two reservoirs, Lake Ogallala and Lake McConaughy, in western Nebraska. Partitioned by season of capture and 50-mm length-classes, walleyeWrwas compared with the abundance of prey fish by length-class. WalleyeWrchanged seasonally and was heavily influenced by prey size availability. In Lake Ogallala, where smaller prey were abundant, there was no significant difference inWracross length-classes by fall. In Lake McConaughy, where more than 90% of all prey fish were over 170 mm, there was a distinct trend by fall. Small walleyes (250–400 mm) exhibited the lowestWr(92.0 ± 0.84); and large walleyes (550–700 mm) had the highestWr(104.0 ± 1.57). Examining changes in walleyeWramong length-classes across seasons was more informative than using a mean populationWrbecause it was sensitive to changes in prey availability for individual walleye length-classes. We aggregated adjacent walleye length-classes with similarWrvalues to formWr-groups to determine the length-groups that were experiencing prey limitations. Identifying walleye length-groups with commonWrstructure from standardized fall surveys may be a cost-effective method of detecting prey fish deficiencies in reservoirs.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0628:UOWRWW>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We compared the release-to-adult returns of coded-wire-tagged groups of fall chinook salmonOncorhynchus tshawytschain a 2 × 2 factorial experimental design: subyearlings and yearlings released directly from a hatchery versus those barged below two main-stem hydroelectric dams on the Snake River, Washington. Releases comprised six brood years over a 6-year period. In every release year, chinook salmon released as yearlings performed better than subyearlings; this was true both for returns to the Snake River and for their contribution to Pacific Ocean and lower Columbia River fisheries. We found no significantly consistent differences in rates of return between transported and on-station releases for either age-class. Return rates of both subyearlings and yearlings varied significantly with year of release. Median migration speeds of branded chinook salmon released on-station varied directly with Snake River flows. However, there was no general relation between flow (and attendant spill) in the Snake and lower Columbia rivers and subsequent release-to-adult returns, both for subyearlings and yearlings. Likewise, transportation past two dams did not improve the adult returns of yearlings in low-flow conditions, and it had limited but inconsistent benefits to subyearlings when Snake River flow and spill were low. The advantages of transportation past two main-stem dams were probably offset by ( 1 ) additional handling stress of loading and unloading fish for transportation and (2) the short duration of transport relative to the time required to acclimate to barge hauling. Most notable was the significant variation in annual rates of return: 1,500% for subyearlings and 700% for yearlings. Both age-groups that migrated in 1985 returned at high rates. Transported chinook salmon strayed to freshwater areas outside the Snake River basin at a significantly higher rate (5.9%) than those released on-station (0.3%). Conversely, chinook salmon released on-station strayed to locations upstream of the hatchery in the Snake River basin at a higher rate (7.8%) than chinook salmon that were transported (2.4%). Overall, the stray rate for all treatment groups to locations outside the Snake River basin was 1.8%.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0638:AROSAY>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We reviewed research conducted by the U.S. National Marine Fisheries Service from 1968 through 1989 on the benefits of using trucks and barges to transport migrating juvenile Chinook salmonOnchorhynchus tsawytschafrom the Snake River around dams and reservoirs in the lower Snake and Columbia rivers. Early results from studies that used trucks indicated that Chinook salmon benefited from transportation: therefore, transportation was adopted as a management strategy by the late 1970s. Our review shows that large-scale transportation by truck was unlikely to benefit survival of juvenile Chinook salmon. Our results from reviewing more recent studies indicate that the use of barges to transport juvenile Chinook salmon may result in improved survival. Benefits may be lower than previously reported because results may have been biased by experimental design: however, even after we adjusted for those potential violations, results from four of six studies on the use of barges indicated that survival of transported fish was higher than survival of fish left to migrate in-river. Because the improved survival from barging may not be enough to ensure recovery of endangered stocks of Chinook salmon, we recommend that management of Snake River Chinook salmon not rely heavily on any one management technique.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0652:ARAAOT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

I used egg presence–absence for striped bass Morone saxatilis from five Maryland spawning areas during 1955–1992 to develop criteria for assessing whether upper Chesapeake Bay spawning stock was at a level providing high and stable recruitment or below a level where recruitment declines appreciably. Strong year-classes did not occur when the proportion of tows with eggs (Ep) fell below 0.60. and the probability of a poor year-class occurring increased greatly asEpfell below 0.80. Mean recruitment increased and coefficient of variation decreased asEprose from 0.40 to 0.80. Highest mean recruitment and lowest coefficient of variation occurred whenEpwas at or above 0.80. A probability-based assessment of upper Chesapeake Bay spawningstock recovery indicated a high risk that spawning-stock status did not recover in 1994 and a low risk in 1995. Upper Chesapeake BayEp, grew during the late 1950s, was highest and stable during the 1960s, decreased through the 1970s to its nadir in the mid-1980s, and then grew quickly through the early 1990s. StableEpcoincided with annual instantaneous fishing mortality rates (F) of 0.50–0.60; decreasingEpoccurred whenFexceeded 0.75, and increasingEpoccurred whenFwas less than 0.25.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0663:UOEPAT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We used telemetry to determine the seasonal and summer diel distributions and movement patterns of small (≤2.4 kg) and large (≥2.9 kg) striped bassMorone saxatilisin Robert S. Kerr Reservoir. Oklahoma. Throughout all seasons striped bass exhibited limited distribution and movements. Rates of movement for all fish in spring 1993 were significantly greater than those in summer 1993, but were similar to those in winter 1993, autumn 1993, or winter 1994. In August 1993, large fish moved farther and were more active during diel tracking than small fish. Striped bass displayed strong fidelity to the Illinois River throughout the study, with 65% of all fish locations occurring in this tributary. Because of their limited movements and distribution, and fidelity to the Illinois River, this population is potentially susceptible to overfishing.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0677:SBDMAS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Protecting sport fish consumers from exposure to chemical contaminants has become an important concern of sport fish managers and state public health agencies. Voluntary fish consumption advisories are often used to convey warnings. Although consumption advisories have been used as a management practice for the past two decades, very little research has been undertaken to evaluate their effectiveness. As part of a statewide survey, a subsample of 1,667 licensed Maine anglers were mailed a questionnaire to examine the effect that a sport fish consumption advisory had on open-water anglers' fishing behavior, consumption patterns, and angler benefits as measured by net economic value. The majority of resident anglers knew about the advisory, but the majority of nonresident anglers did not. Of all anglers who knew about the advisory, less than 25% changed their fishing behavior. Our data suggest that most anglers were in a low-risk group and may have been in compliance with the consumption guidelines; however, over half of the at-risk female anglers may have been in noncompliance with the guidelines.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0687:EOASSF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Several states in the USA have proposed or implemented new regulations to monitor recreational fishing more closely. One regulatory tool, the saltwater recreational fishing license, has been adopted in several states, yet in other states it is opposed heavily by fishers. One difficulty in developing new types of saltwater licenses in North Carolina is that part-time fishers use commercial gear but straddle recreational and commercial fishing motives and behaviors. In North Carolina, over 20,000 people hold commercial fishing licenses, but fewer than 10% of those (1,747) sell more than US$ 10,000 worth of seafood annually. North Carolina's undocumented recreational trawl fishery for shrimp (Penaeidae) often harvests significant fishery resources but has inadequate or loosely enforced restrictions. To investigate the nature of the recreational shrimp trawl fishery in coastal North Carolina waters, we conducted an intercept interview survey in the fall of 1995. Slightly more than half of those interviewed were recreational shrimpers, and the remainder were part-time commercial shrimpers. All were men, and most held skilled and semi-skilled technical jobs. Most limited their shrimping activities to local waters and had used other commercial gear including gill nets, clam rakes, scallop and oyster dredges, and crab pots. Part-time commercial shrimpers spent more time fishing, caught more shrimp. and had shrimped more in previous years than recreational shrimpers: however, only 18% of all shrimpers fished exclusively for shrimp. About one-third of part-time commercial shrimpers interviewed shrimped primarily for personal consumption, while about two-thirds sold all or part of their catch. Although about 90% of all gear was equipped with a bycatch reduction device (BRD), placement of the BRD was highly variable, which suggests a need to standardize BRD placement to increase its effectiveness.

ISSN:0275-5947    

DOI:10.1577/1548-8675(1997)017<0696:PCOTNC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor