Showing papers in "North American Journal of Fisheries Management in 1988"
TL;DR: In this article, trends in abundance of spring and summer chinook salmon Oncorhynchus tshawytscha and steelhead Salmo gairdneri returning to the Snake River and mid-Columbia River above Priest Rapids Dam were determined by analyzing the percentage of adults returning from the smolt out-migrations of 1962-1984.
Abstract: Trends in abundance of spring and summer chinook salmon Oncorhynchus tshawytscha and steelhead Salmo gairdneri returning to the Snake River and mid-Columbia River above Priest Rapids Dam were determined by analyzing the percentage of adults returning from the smolt out-migrations of 1962–1984. Runs declined as a result of hydroelectric development of the river; the main cause for the decline was the mortality of juveniles migrating downstream through as many as nine dams and impoundments en route to the ocean. Mid-Columbia River summer chinook salmon runs experienced the greatest decline because of higher mortalities incurred during their migration to sea as subyearlings in July and August. Mortality was lower for remaining races of fish that migrate to sea as yearlings in the spring during higher river flows, more spill at dams, and cooler water temperatures. Enhancement measures to offset dam-related mortality of smolts began in 1970 on the Snake River and in 1975 on the mid-Columbia River. The...
208 citations
TL;DR: On-site interviews and a mail questionnaire survey of 377 anglers on two Virginia rivers were used to evaluate the concept of recreational specialization for differentiating angler subgroups, and highly specialized anglers were likely to cite resource-related motives.
Abstract: On-site interviews and a mail questionnaire survey of 377 anglers on two Virginia rivers were used to evaluate the concept of recreational specialization for differentiating angler subgroups. Specialization was defined for four dimensions of angler behavior: (1) fishery resource use, (2) experience, (3) investment, and (4) centrality of angling to lifestyle. Six types of anglers, representing low to high levels of specialization, were identified by cluster analysis. The experience dimension was the most important contributor to the framework, accounting for 24% of the variance in the data. A combination of the resource, investment, and centrality dimensions explained 48% of the variance. Highly specialized anglers were likely to cite resource-related motives (e.g., trophy fish), to rely on skill to catch fish, to prefer to catch and release larger fish, and to favor restrictive harvest regulations. Less specialized anglers cited escape and family-oriented recreation as motivations for fishing, pl...
183 citations
TL;DR: Electrofishing could bias mark–recapture studies of large rainbow trout, and electrofishing in waters containing endangered or threatened species should be considered with great caution.
Abstract: Adult rainbow trout Salmo gairdneri captured by electrofishing were analyzed for spinal injury by X-ray photography and autopsies. The effects of three electrical pulse shapes were compared. Of 209 fish captured, 50% suffered spinal injuries involving an average of eight vertebrae that were dislocated, splintered, or both. One-quarter-sine wave pulses injured a significantly higher proportion of fish (67%) than either exponential pulses (44%) or square wave pulses (44%; P < 0.05). Quarter-sine waves also damaged significantly more vertebrae per fish (average, 9.5) than did exponential pulses (6.6); the average number damaged by square waves (8.2) did not differ significantly from either of the other means. Electrofishing could bias mark–recapture studies of large rainbow trout. Electrofishing in waters containing endangered or threatened species should be considered with great caution.
111 citations
TL;DR: In this article, the authors describe the magnitude of fluctuations in trout populations in several widely separated streams in the intermountain region of the western United States, and consider the potential effect of such fluctuations on land-management planning.
Abstract: We describe the magnitude of fluctuations in trout populations in several widely separated streams in the intermountain region of the western United States, and consider the potential effect of such fluctuations on land-management planning. Trout populations included native and exotic species, self-reproducing and hatchery-maintained populations, and assemblages that ranged from monospecific to diverse. Annual fluctuations in population statistics were generally large, and some fluctuations were related to geographic setting and trout species. For individual species, fluctuations in all statistics were typically less in the Rocky Mountain study areas than in the Great Basin, but, for the total salmonid community, the situation was reversed. Numerical population fluctuations frequently did not parallel fluctuations in biomass. Except in cases of irregular occurrence, populations of brook trout Salvelinus fontinalis, particularly those in Rocky Mountain study areas, were numerically the most stable...
107 citations
TL;DR: In this paper, the authors grouped eight warmwater fishes, each represented by one to four life stages, into habitat-use guilds (i.e., groups of species) to select target species for instream flow studies.
Abstract: We grouped eight warmwater fishes, each represented by one to four life stages, into habitat-use guilds (i.e., groups of species) to select target species for instream flow studies. Cluster analysis of depth, velocity, substrate, and cover use identified four primary habitat-use guilds, which were distinguished largely on the basis of water velocity. Habitat-suitability criteria were developed for each species and life stage combination, and these criteria were used in physical habitat simulations to determine relations between weighted usable area (WUA) and discharge for three streams in the upper James River basin, Virginia. Weighted usable areas for species within each habitat-use guild generally exhibited similar responses to discharge except those for some stream-margin inhabitants and for strongly cover-oriented species. Four types of habitat–discharge relations, which were consistent among streams, were identified. Curves of WUA versus discharge for habitat generalists and some specialists...
105 citations
TL;DR: Because angling affects populations, management steps to reduce angling mortality of larger fish, as well as to reduce density of small fish, seem desirable.
Abstract: Angling would affect a fish population if it increased the total mortality rate, reduced numbers or biomass, or reduced the average size of fish in a population by removing the larger ones. Data from the literature indicate that angling commonly affects populations of bluegills Lepomis macrochirus. Substantial exploitation rates (mean, 27%) are not unusual; exploitation is directly related to fishing effort, and angling reduces average size and increases total mortality. Many exploited bluegill populations comprise mainly small fish, less than 150 mm long. Consistent high recruitment of young of the year, size-selective exploitation, and reduced growth and increased natural mortality from competition would tend to produce and maintain such a population size structure. Because angling affects populations, management steps to reduce angling mortality of larger fish, as well as to reduce density of small fish, seem desirable.
93 citations
TL;DR: It is indicated that different sizes and mixtures of sediment can affect egg survival differently, and no definitive relationship was found between sediment size and concentration, and alevin and fry quality.
Abstract: We compared, in the laboratory, egg survival, and alevin and fry size of steelhead Oncorhyncus mykiss (formerly Salmo gairdneri) and chinook salmon O. tshawytscha after incubations in 16 mixtures of two distinct size-classes of sediment. Fine sediments were less than 0.84 mm in diameter, and coarse sediments were 0.84–4.6 mm in diameter. We incubated recently fertilized and eyed steelhead eggs and chinook salmon eggs in Whitlock–Vibert boxes placed in controlled-flow channels. Egg survival in both sediment types was inversely related to the percentage of sediments within the incubation gravel; the poorest survival occurred in fine sediments. Percentage egg survival was positively related to intragravel water velocities, which ranged from 36 to 1,550 cm/h. No definitive relationship was found between sediment size and concentration, and alevin and fry quality. Overall, our results indicated that different sizes and mixtures of sediment can affect egg survival differently. The results confirmed tha...
86 citations
TL;DR: In this article, a technique for approximating confidence intervals for stock density and related indices is presented along with recommendations for its use, which allows easy approximation of confidence intervals by use of tables or a simple equation.
Abstract: Proportional stock density and related indices are frequently used to describe the size structure of fish populations. A technique for approximating confidence intervals for these indices is presented along with recommendations for its use. This method allows easy approximation of confidence intervals by use of tables or a simple equation.
85 citations
TL;DR: An important mixed-stock fishery for striped bass off the northeastern USA has focused the majority of stock discrimination efforts on identification of Atlantic coast populations.
Abstract: Attempts to discriminate stocks of striped bass Morone saxatilis have spanned five decades. We review and evaluate the approaches used, outline research trends, and suggest research needs and potential future applications of stock discrimination techniques. There have been moderate gains over the years in the ability to discriminate among stocks, primarily due to the use of biochemical techniques. An important mixed-stock fishery for striped bass off the northeastern USA has focused the majority of stock discrimination efforts on identification of Atlantic coast populations. Many techniques have been applied alone or in combination. Phenotypic studies have involved the presence of specific parasites, meristic and morphometric characters, trace element composition of scales, scale morphology, and densitometric analysis of isoelectrically focused eye lens proteins. Genotypic techniques have included cytogenetics, protein electrophoresis, isoelectric focusing, restriction endonuclease analysis of mi...
76 citations
TL;DR: In this article, the authors found that distance transferred from the natal stream was negatively related to recovery rate (recruits per gram of juveniles released) for hatchery-reared coho salmon Oncorhynchus kisutch.
Abstract: Distance transferred from the natal stream was negatively related to recovery rate (recruits per gram of juveniles released) for hatchery-reared coho salmon Oncorhynchus kisutch. This relation, which reflects the important influence of genetic adaptation and genetic differences among stocks on recovery rates and survival, should be useful in deciding whether or not to transfer fish.
66 citations
TL;DR: In this article, an inexpensive and simple grinding technique was described to section otoliths that were used to determine the ages of both freshwater and marine fish, depending on their size, 6-15 Otoliths can be sectioned and their annuli counted, per hour.
Abstract: This paper describes an inexpensive and simple grinding technique to section otoliths that I have used to determine the ages of both freshwater and marine fish. Depending on their size, 6–15 otoliths can be sectioned, and their annuli counted, per hour.
TL;DR: Estimates of estimated ages from vertebrae, cleithra, opercular bones, otoliths, and scales were measured in replicated trials on samples from lake trout Salvelinus namaycush from interior Alaska to determine the age of immature and mature lake trout.
Abstract: Precisions of estimated ages from vertebrae, cleithra, opercular bones, otoliths, and scales were measured in replicated trials on samples from lake trout Salvelinus namaycush from interior Alaska. Ages from all structures were similar for sexually immature lake trout. For mature lake trout, estimated ages from otoliths and from opercular bones were the most precise, although ages from opercular bones were significantly younger by a year than ages from otoliths. Estimated ages from cleithra and whole vertebrae were, respectively, too imprecise and too low for these structures to be useful in age validation studies. On this basis, otoliths and opercular bones can be used in age validation studies and scales can be used to estimate the age of immature lake trout.
TL;DR: Habitat selection by age-0 hybrids was similar to that of walleye, except hybrids preferred finer substrates in fall, and older hybrids and walleyes moved offshore at temperatures above 22°C.
Abstract: We compared habitat preferences, survival, growth, foods, and harvests of stocked walleyes Stizostedion vitreum and walleye ♀ × sauger S. canadense ♂ hybrids in Pleasant Hill Reservoir, Ohio. Both fishes were stocked at similar rates and sizes (about 40 mm mean total length) in late May or early June 1979–1982. Neither group showed consistently better survival. Growth was similar until age 2. Thereafter, hybrids grew faster than walleyes. Age-0 walleyes occurred mostly over fine substrates in early summer and coarse substrates by fall. Habitat selection by age-0 hybrids was similar to that of walleyes, except hybrids preferred finer substrates in fall. Older hybrids and walleyes moved offshore at temperatures above 22°C. Diets of both fishes were similar, but hybrids ate more littoral fishes, whereas walleyes ate more pelagic fishes. Age-1 and older hybrids and walleyes ate mostly invertebrates in spring. Age-0 gizzard shad Dorosoma cepedianum were the most important prey for all ages of both gro...
TL;DR: In this paper, the authors describe size selectivity of five types of gear and potential bias in estimates of population statistics of smallmouth bass, walleye, Stizostedion vitreum, and northern squawfish in John Day Reservoir on the Columbia River.
Abstract: We describe size selectivity of five types of gear, size selectivity in combined gear samples, and potential bias in estimates of population statistics of smallmouth bass Micropterus dolomieui, walleye Stizostedion vitreum, and northern squawfish Ptychocheilus oregonensis in John Day Reservoir on the Columbia River. We sampled from 1983 to 1986 with two types of gill nets, boat electrofishers, trap nets, and rod and reel. Different gears selectively sampled different sizes of each species. Recapture rates indicated that different sizes of fish remained differentially vulnerable to capture even when samples from all gears were pooled. Vulnerability of smallmouth bass declined with increasing size. Vulnerability of walleye was not related to size. Vulnerability of northern squawfish increased with size. Size selectivity of gear resulted in estimates of abundance potentially biased by 2–16%, estimates of proportional stock density (size structure) biased by 11–46%, and estimates of annual rate of mo...
TL;DR: Indications are that addition of a water conditioner to live wells enhances survival of angled largemouth bass and postrelease fish was higher when water temperatures were cool during fall and winter than for those held in unconditioned water.
Abstract: Survival of angled largemouth bass Micropterus salmoides held in live wells for 3–9 h, with and without a water conditioner, was compared to largemouth bass released within 30 min (immediate release) of capture. The study was set up to simulate conditions that may occur during a largemouth bass tournament. Simulated tournaments were held in August, November, February, May, and July. Survival of prerelease and postrelease fish was higher when water temperatures were cool during fall and winter. Survival of largemouth bass released within 30 min was 98.9%, which was higher (P < 0.01) than survival of fish held in live wells without a water conditioner (90.8%). Fish held for 3–9 h in live wells with a water conditioner had a 96.5% survival, which was higher (P < 0.05) than survival for those held in unconditioned water. Largemouth bass caught in July had higher mortality than fish caught in November, February, or May. Indications are that addition of a water conditioner to live wells enhances surviv...
TL;DR: It is found that in the presence of an established predator population and adequate forage, even the largest size-group of channel catfish suffered 55 and 73% natural mortality, after one and two growing seasons, respectively.
Abstract: The survival, angler catch, and harvest of several size-groups of channel catfish Ictalurus punctatus, concurrently stocked into a 6.1-hectare impoundment in central Illinois, increased with size at stocking. However, in the presence of an established predator population and adequate forage, even the largest size-group of channel catfish (mean length, 202 mm total length) suffered 55 and 73% natural mortality, after one and two growing seasons, respectively. Based on the results of this study, the greatest return on investment would be obtained by stocking fish of at least 200 mm total length.
TL;DR: In this paper, the authors found that gill Na+,K+-ATPase levels were significantly higher in fish guided into the gatewell than in those not guided, suggesting that there is a relationship between the physiological status of smolting yearling chinook salmon and their susceptibility to guidance by traveling screens.
Abstract: Several hydroelectric dams in the Snake-Columbia river system are equipped with submersible traveling screens that project into the turbine intakes. The screens are designed to divert juvenile migrant Pacific salmon Oncorhynchus spp. and steelhead Salmo gairdneri from the intake upward into gatewells and the ajoining central bypass system. Assays ofgill Na+,K+-ATPase were performed on yearling chinook salmon O. tshawytscha collected during several routine fish guidance efficiency tests in 1985 and 1986. On three of the four sampling dates, gill Na+,K+-ATPase levels were significantly higher in fish guided into the gatewell than in those not guided. These data suggest there is a relationship between the physiological status of smolting yearling chinook salmon and their susceptibility to guidance by traveling screens. Assessments of salmonid out-migrations may be biased if they are based on samples from traveling-screen guidance systems.
TL;DR: A 4-year study of a montane stream from which cattle grazing had been excluded for 10 years indicated that stream bank vegetation and stability were markedly improved and that stream substrate fines were somewhat reduced, but it indicated that fish populations were unaffected as discussed by the authors.
Abstract: A 4-year study of a montane stream from which cattle grazing had been excluded for 10 years indicated that stream bank vegetation and stability were markedly improved and that stream substrate fines were somewhat reduced, but it indicated that fish populations were unaffected. Shortcomings of this case history study are common to past similarly designed studies of grazing effects on fishes and their habitats. Three major deficiencies in research design are (1) lack of pretreatment data, (2) improper consideration of fishery management principles, and (3) linear positioning of treatments along a stream. Future research on riparian grazing effects must address these factors in addition to designs of long-term (10+ years) ecosystem (watershed) studies.
TL;DR: It is concluded that, in large clear streams with little cover, the snorkel-expansion method provides a quick, reliable density of westslope cutthroat trout in the Flathead River.
Abstract: The abundance of westslope cutthroat trout Salmo clarki lewisi was estimated in three sections of the South Fork of the Flathead River. We made two different Petersen mark–recapture estimates (angling only and angling with snorkeling) and compared them to a snorkel-expansion estimate. Anglers caught and snorkelers classified similar size-groups ofcutthroat trout. The snorkel-expansion estimate was similar to the two Petersen estimates. In one section, we estimated total abundance at 452, 527, and 546 cutthroat trout/km by the hook-and-line Petersen, snorkel-Petersen, and snorkel-expansion methods, respectively. In a second section, we estimated 215 and 221 cutthroat trout/km by the snorkel-Petersen and snorkel-expansion methods, respectively. In a third section, we estimated 183 and 201 cutthroat trout/km by the snorkel-Petersen and snorkel-expansion methods, respectively. We concluded that, in large clear streams with little cover, the snorkel-expansion method provides a quick, reliable density ...
TL;DR: The results were attributable to specific differences in activity patterns and net-saturation effects and it was concluded that use of gill-net catches as indices offish abu...
Abstract: The effects of varying net length and set time on fish catches in gill nets were studied at two sites in the Bay of Quinte, Lake Ontario. A latin square design was used (four locations per site over four nights); either net length was varied, from 25 to 200 yd over 12 h, or set time was varied, from 1.5 to 12 h with 50 yd of net. Treatment, location, and date effects on catches from each site were analyzed by a multiple regression model. Net length effects on catch per unit of effort (CPUE) were negligible for total and some fish species catches; CPUE for walleyes Stizostedion vitreum decreased with increasing net length. Set-time effects on total CPUE were significant; the CPUE of white perch Morone americana increased with set time, but CPUEs for yellow perch Perca flavescens, alewives Alosa pseudoharengus, and walleyes decreased. The results were attributable to specific differences in activity patterns and net-saturation effects. We concluded that use of gill-net catches as indices offish abu...
TL;DR: Survival of Atlantic salmon Salmo salar between fertilization and emergence was monitored in Northern Stream, Washington County, Maine and decreased rapidly after hatching to only 2% at emergence.
Abstract: Survival of Atlantic salmon Salmo salar between fertilization and emergence was monitored in Northern Stream, Washington County, Maine. Green eggs were buried in modified Whitlock–Vibert egg boxes and survival was estimated on five occasions–four before emergence and one at emergence. Survival was 74% through hatching, but decreased rapidly after hatching to only 2% at emergence.
TL;DR: In this article, the authors monitored the movements of 23 northern squawfish Ptychocheilus oregonensis below a Columbia River hydroelectric dam during the out-migration of juvenile anadromous salmonids in 1984 and 1985.
Abstract: The movements of 23 northern Squawfish Ptychocheilus oregonensis were monitored by radiotelemetry below a Columbia River hydroelectric dam during the out-migration of juvenile anadromous salmonids in 1984 and 1985. The work was done as part of a study to relate predator abundances and distribution to juvenile salmonid mortalities associated with dams. Northern Squawfish remained in protected shoreline areas in spring and early summer, when discharge rates were high, but moved close to the dam and the juvenile bypass outflow area in mid to late summer, when discharge rates were low. Trends in northern Squawfish movements were similar during abrupt changes in discharge rate. During short-term closures of the spillway, when flow patterns were abruptly changed, four of five northern Squawfish moved out of protected areas and into the main river channel. Surface water velocities at 81 locations occupied by radio-tagged northern Squawfish in June to August 1985 ranged from 0 to 70 cm/s (mean, 24.5 cm/s...
TL;DR: In this article, the authors determine sample sizes needed to use t-tests to detect changes in indices of angling effort, catch per unit effort (CPUE), fish length, fish growth, and fish age.
Abstract: The purpose of this paper is to determine sample sizes needed to use t-tests to detect changes in indices of angling effort, catch per unit effort (CPUE), fish length, fish growth, and fish age. The results are presented in graphs of sample size versus detectable change for data from small trout lakes in southern British Columbia. Sample size requirements are most difficult to meet for indices of CPUE, effort, and age, but the cost of data acquisition appears reasonable even for small lakes with less than 1,000 angler-days/year. Alternative choices for significance levels (0.01–0.20) and power (0.80–0.95) result in almost a six-fold variation in sample size requirements.
TL;DR: Under the most cost-effective hatchery regime for producing lake trout (the maximum number of SY plus some FF to fully utilize hatchery space and personnel year round), rearing c...
Abstract: We made 16 paired releases of lake trout Salvelinus namaycush of four year classes (1979–1982) at five locations to compare survival and growth of hatchery-reared fish stocked as fall fingerlings (FF) and as spring yearlings (SY). Comparisons were based on fish at ages 2–8 recovered with bottom trawls, with gill nets, and from anglers' catches. Mean lengths and weights were greater for SY than for FF at all ages, and SY attained sexual maturity at an earlier age than FF. The survival of FF may have been affected by average size at stocking and by the severity of the weather during the first winter after stocking. Survival ratios of SY to FF lake trout from stocking to age 2 ranged from 1.32:1 to 6.80:1, and a ratio of 2.41:1 was considered to be typical. Stocking cost per 1,000 fish was US$21.76 for FF and $35.45 for SY. Under the most cost-effective hatchery regime for producing lake trout (the maximum number of SY plus some FF to fully utilize hatchery space and personnel year round), rearing c...
TL;DR: It is hypothesized that pulse production of H. limbata in even-numbered years positively affects walleye recruitment by enhancing egg production by adult walleyes and buffering young of the year against predation and cannibalism.
Abstract: Young-of-the-year walleyes Stizostedion vitreum are more abundant in even-numbered years than in odd-numbered years in Savanne Lake, Ontario. Differences among years were related to emergences of the burrowing mayfly Hexagenia limbata. Adult walleyes from evennumbered year classes are more abundant than those from odd-numbered year classes. We hypothesize that pulse production of H. limbata in even-numbered years positively affects walleye recruitment by enhancing egg production by adult walleyes and buffering young of the year against predation and cannibalism.
TL;DR: In 7 of 26 experiments, survival of tagged fish was significantly different from (usually lower than) survival of control fish (P < 0.05); after 6–9 months, tag retentions varied from 91 to 100%.
Abstract: We examined the feasibility of implanting coded wire tags in several size-classes (47–189 mm, total length) of channel catfish Ictalurus punctatus, bluegill Lepomis macrochirus, walleye Stizostedion vitreum, largemouth bass Micropterus salmoides, and golden shiner Notemigonus crysoleucas. Tags were implanted in three anatomical locations (nasal capsule, cheek musculature, or nape). Growth of tagged and untagged fish was not significantly different, and tag-related mortalities ranged from 0 to 12% throughout the study. In 7 of 26 experiments, survival of tagged fish was significantly different from (usually lower than) survival of control fish (P < 0.05). After 6–9 months, tag retentions varied from 91 to 100%.
TL;DR: Fish in Henderson and Savanne lakes, boreal lakes located near Thunder Bay, Ontario, were experimentally exploited for 6 years by different harvest strategies, showing statistically significant annual increases in fecundity since the start of exploitation.
Abstract: Fish in Henderson and Savanne lakes, boreal lakes located near Thunder Bay, Ontario, were experimentally exploited for 6 years by different harvest strategies The adult population of walleyes Stizostedion vitreum in Henderson Lake, estimated from trap nets, was drastically reduced over a period of 3 years, from 1,336 to 375 fish; exploitation rates ranged from 25 to 65% In Savanne Lake, intermediate-size walleye (25–54 cm total length) were harvested for 5 years; yield was slightly less than the average adult production The walleye population was reduced from 5,595 to 4,206 fish by exploitation rates of 12–16% Both populations have shown statistically significant annual increases in fecundity since the start of exploitation Yearly fluctuations in fecundity, especially of older fish, were noted in both lakes; high values occurred in even-numbered years and low values in odd-numbered years We hypothesize that these fecundity changes reflect food availability, particularly alternate-year fluct
TL;DR: A 305mm minimum-length limit on angler catches of smallmouth bass Micropterus dolomieui was evaluated in 1982 and 1983 by comparing populations in a section of the New River in Virginia, and a section in West Virginia, where there was no length limit as discussed by the authors.
Abstract: A 305-mm minimum-length limit on angler catches of smallmouth bass Micropterus dolomieui was evaluated in 1982 and 1983 by comparing populations in a section of the New River in Virginia, where the limit was applied, and a section in West Virginia, where there was no length limit. Smallmouth bass at age 4 averaged 281 mm total length in the Virginia section and 331 mm in the West Virginia section. Condition of smallmouth bass, as measured by relative weight (W r), was significantly greater for West Virginia fish for most size categories in both years. Survival estimates for both sections of the New River were low (less than 24%); survival was generally lower for the Virginia population. Proportional stock density values (1.8–5.1% for both sections) were not significantly different between sections. The minimum-length limit has not improved fishing, as measured by catch rates or population size structure, in the Virginia section of the New River. New regulations should be adopted in both sections ...
TL;DR: Failure to demonstrate a treatment effect in either experiment suggests that electrofishing does not adversely affect the short-term survival of mottled sculpin, and similar result was obtained for several other species of stream fishes.
Abstract: We examined the effects of electrofishing on the survival of mottled sculpin Cottus bairdi in two experiments. Three tanks each were filled with mottled sculpin collected by electrofishing (treatment) and by kick-seining (control). We maintained these tanks for at least 30 d and recorded all deaths. Patterns of survival were not significantly different among tanks in either of the experiments. In addition, there were no significant differences between pooled data sets (all control tanks versus all treatment tanks) within each experiment. Failure to demonstrate a treatment effect in either experiment suggests that electrofishing does not adversely affect the short-term survival of mottled sculpin. Although sample sizes were insufficient for statistical analysis, a similar result was obtained for several other species of stream fishes. To test the effects of multiple electrofishing exposures, we conducted another experiment in four artificial stream sections. Treatment mottled sculpin were shocked,...
TL;DR: Investigating the stock origins of chinook salmon in incidental catches by foreign and joint-venture groundfish vessels operating in the Bering Sea portion of the U.S. exclusive economic zone found Western Alaska, which included Canadian Yukon fish, was the predominant regional stock in most age-group, time, and area strata.
Abstract: An estimated 386,946 chinook salmon Oncorhynchus tshawytscha were taken in incidental catches by foreign and joint-venture groundfish vessels operating in the Bering Sea portion of the U.S. exclusive economic zone, 1977–1986. Concern about the effect of incidental catches on the salmon fisheries of western Alaska provided the impetus for a study to determine the stock origins of chinook salmon in these catches. The proportions of regional (Asia, western Alaska, central Alaska, and southeast Alaska–British Columbia) and western Alaskan subregional (Yukon, Kuskokwim, and Bristol Bay) stocks of Chinook salmon in 1979, 1981, and 1982 samples collected by U.S. foreign fishery observers were estimated by scale pattern analysis. Estimated proportions ofthe regional stocks averaged 60% western Alaska, 17% central Alaska, 14% Asia, and 9% southeast Alaska-British Columbia. Western Alaska, which included Canadian Yukon fish, was the predominant regional stock in most age-group, time, and area strata. Stock...