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At least 721 records · Page 40Linked to original sources

Can pelagic forage fish and spawning cisco (Coregonus artedi) biomass in the western arm of Lake Superior be assessed with a single summer survey?

Management efforts to rehabilitate lake trout Salvelinus namaycush in Lake Superior have been successful and the recent increase in their numbers has led to interest in measuring biomass of pelagic prey fish species important to these predators. Lake Superior cisco Coregonus artedi currently support roe fisheries and determining the sustainability of these fisheries is an important management issue. We conducted acoustic and midwater trawl surveys of the western arm of Lake Superior during three periods: summer (July-August), October, and November 2006 to determine if a single survey can be timed to estimate biomass of both prey fish and spawning cisco. We evaluated our methods by comparing observed trawl catches of small (<250 mm total length) and large fish to expected trawl catches based on acoustic densities in the trawl path. We found the relationship between observed and expected catches approached unity over a wide range of densities, suggesting that our acoustic method provided reasonable estimates of fish density, and that midwater trawling methods were free of species- and size-selectivity issues. Rainbow smelt Osmerus mordax was by number the most common species captured in the nearshore (<80 m bathymetric depth) stratum during all three surveys, while kiyi Coregonus kiyi was predominant offshore except during November. Total biomass estimates of rainbow smelt in the western arm were similar during all three surveys, while total biomass of kiyi was similar between summer and October, but was lower in November. Total biomass of large cisco increased substantially in November, while small bloater Coregonus hoyi biomass was lower. We compared our summer 2006 estimates of total fish biomass to the results of a summer survey in 1997 and obtained similar results. We conclude that the temporal window for obtaining biomass estimates of pelagic prey species in the western arm of Lake Superior is wide (July through October), but estimating spawning cisco abundance is best done with a November survey.

Fisheries Research↗

Vertical transmission of infectious haematopoietic necrosis virus in sockeye salmon, Oncorhynchus nerka (Walbaum): isolation of virus from dead eggs and fry

The control of epizootics of infectious haematopoietic necrosis (IIHN) virus in salmonid fishes is presently based on examination and certification of adult brood fish to prevent the introduction of virus-infected eggs into hatcheries (Canadian Fisherics and Marine Service 1976; McDaniel 1979). This strategy is based on the assumption that the virus is vertically transmitted in association with the gametes. However, evidence for vertical transmission of lHN virus is circumstantial, based mostly on the appearance of the disease outside the enzootic area (the west coast of North America) in fish hatched from eggs obtained from within that area (Plumb 1972; Holway & Smith 1973; Wolf, Quimby, Pettijohn & Landolt 1973, Sano, Nishimura, Okamoto, Yamazaki, Hanada & Watanabe 1977. Carlisle, Schat & Elston 1979). An indirect demonstration of vertical transmission was made by placing known virus-free fish in the water above and below raceways containing fish that suffered an IEEN epizootic in an cffort to climinate waterborne virus as a source of infection (Wingficid & Chan 1970). The fish placed below the raceway developed IHN, due to waterborne virus released from the affected fish in the raceway, but the fish placed above the raceway failed to develop IHN. These results suggested that the source of infection of the fish in the raceway was not the water supply, although it is possible that the virus was no longer present in the water supply at the time the sentinel fish were exposed to the water.

Journal of Fish Diseases↗

Capture versus tagging impacts on chum salmon freshwater spawning migration travel times

The spawning migration travel times of chum salmon, Oncorhynchus keta (Walbaum), fitted with gastrically implanted radio tags vs external spaghetti tags were tested for a short [≈60 river km (rkm)] and long migration route (≈730 rkm) on the Koyukuk River, Alaska, USA. Using a novel application of statistical arrival curve models to infer travel times for uncaptured fish, migrations by chum salmon not directly handled during the study were also assessed. Results demonstrated negligible differences in travel times within migration routes between fish fitted only with spaghetti tags and fish fitted with radio tags, indicating low impacts on migration travel behaviour associated with gastric tags once deployed. Conversely, travel times for unhandled fish as inferred by statistical arrival models may have been 12%–24% shorter than those for fish captured with gillnets for tagging. These results suggest that, if present, chum salmon migration behaviour impacts may be more strongly associated with fish capture than tag deployment.

Fisheries Management and Ecology↗

FishTraits: a database of ecological and life-history traits of freshwater fishes of the United States

The need for integrated and widely accessible sources of species traits data to facilitate studies of ecology, conservation, and management has motivated development of traits databases for various taxa. In spite of the increasing number of traits-based analyses of freshwater fishes in the United States, no consolidated database of traits of this group exists publicly, and much useful information on these species is documented only in obscure sources. The largely inaccessible and unconsolidated traits information makes large-scale analysis involving many fishes and/or traits particularly challenging. We have compiled a database of > 100 traits for 809 (731 native and 78 nonnative) fish species found in freshwaters of the conterminous United States, including 37 native families and 145 native genera. The database, named Fish Traits, contains information on four major categories of traits: (1) trophic ecology; (2) body size, reproductive ecology, and life history; (3) habitat preferences; and (4) salinity and temperature tolerances. Information on geographic distribution and conservation status was also compiled. The database enhances many opportunities for conducting research on fish species traits and constitutes the first step toward establishing a central repository for a continually expanding set of traits of North American fishes.

Fisheries↗

Relation between distance transferred from natal stream and recovery rate for hatchery coho salmon, Oncorhynchus kisutch

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.

North American Journal of Fisheries Management↗

Efficacy of benzocaine as an anesthetic for salmonid fishes

Benzocaine was tested in the laboratory to determine the effective concentrations for anesthetizing juvenile chinook salmon Oncorhynchus tshawytscha and rainbow trout O. mykiss (formerly Salmo gairdneri ). Tests were conducted at three water temperatures, in waters ranging from very soft to very hard, and with groups of rainbow trout from 5 to 47 cm long and chinook salmon 20 cm long. Effective concentrations were defined as those that rendered the fish fully handleable in 3 min or less, allowed recovery of most fish within 10 min, and caused no mortality after 15-min exposures. Concentrations of 25–45 mg/L anesthetized both species over the entire range of conditions tested. Although efficacy was essentially unrelated to species or water quality, it was related to water temperature and size offish; the concentrations of benzocaine required were highest at the lowest water temperatures and for the largest fish.

North American Journal of Fisheries Management↗

Incidental catch of marine birds in the north pacific high seas driftnet fisheries in 1990

The incidental take of marine birds was estimated for the following North Pacific driftnet fisheries in 1990: Japanese squid, Japanese large-mesh, Korean squid, and Taiwanese squid and large-mesh combined. The take was estimated by assuming that the data represented a random sample from an unstratified population of all driftnet fisheries in the North Pacific. Estimates for 13 species or species groups are presented, along with some discussion of inadequacies of the design. About 416,000 marine birds were estimated to be taken incidentally during the 1990 season; 80% of these were in the Japanese squid fishery. Sooty Shearwaters, Short-tailed Shearwaters, and Laysan Albatrosses were the most common species in the bycatch.Regression models were also developed to explore the relations between bycatch rate of three groups--Black-footed Albatross, Laysan Albatross, and 'dark' shearwaters--and various explanatory variables, such as latitude, longitude, month, vessel, sea surface temperature, and net soak time (length of time nets were in the water). This was done for only the Japanese squid fishery, for which the most complete information was available. For modelling purposes, fishing operations for each vessel were grouped into 5-degree blocks of latitude and longitude.Results of model building indicated that vessel had a significant influence on bycatch rates of all three groups. This finding emphasizes the importance of the sample of vessels being representative of the entire fleet. In addition, bycatch rates of all three groups varied spatially and temporally. Bycatch rates for Laysan Albatrosses tended to decline during the fishing season, whereas those for Black-footed Albatrosses and dark shearwaters tended to increase as the season progressed. Bycatch rates were positively related to net soak time for Laysan Albatrosses and dark shearwaters. Bycatch rates of dark shearwaters were lower for higher sea surface temperatures.

International North Pacific Fisheries Commission B↗

Pattern detection in stream networks: Quantifying spatial variability in fish distribution

Biological and physical properties of rivers and streams are inherently difficult to sample and visualize at the resolution and extent necessary to detect fine-scale distributional patterns over large areas. Satellite imagery and broad-scale fish survey methods are effective for quantifying spatial variability in biological and physical variables over a range of scales in marine environments but are often too coarse in resolution to address conservation needs in inland fisheries management. We present methods for sampling and analyzing multiscale, spatially continuous patterns of stream fishes and physical habitat in small- to medium-size watersheds (500–1000 hectares). Geospatial tools, including geographic information system (GIS) software such as ArcInfo dynamic segmentation and ArcScene 3D analyst modules, were used to display complex biological and physical datasets. These tools also provided spatial referencing information (e.g. Cartesian and route-measure coordinates) necessary for conducting geostatistical analyses of spatial patterns (empirical semivariograms and wavelet analysis) in linear stream networks. Graphical depiction of fish distribution along a one-dimensional longitudinal profile and throughout the stream network (superimposed on a 10-metre digital elevation model) provided the spatial context necessary for describing and interpreting the relationship between landscape pattern and the distribution of coastal cutthroat trout ( Oncorhynchus clarki clarki ) in western Oregon, U.S.A. The distribution of coastal cutthroat trout was highly autocorrelated and exhibited a spherical semivariogram with a defined nugget, sill, and range. Wavelet analysis of the main-stem longitudinal profile revealed periodicity in trout distribution at three nested spatial scales corresponding ostensibly to landscape disturbances and the spacing of tributary junctions.

Oregon↗

Mixed stock analysis of Lake Michigan's Lake Whitefish Coregonus clupeaformis commercial fishery

Lake whitefish ( Coregonus clupeaformis ) support the primary commercial fishery in Lake Michigan. Discrete genetic stocks of lake whitefish have been identified and tagging data suggest stocks are mixed throughout much of the year. Our objectives were to determine if (1) differential stock harvest occurs in the commercial catch, (2) spatial differences in genetic composition of harvested fish were present, and (3) seasonal differences were present in the harvest by commercial fisheries that operate in management zones WI-2 and WFM-01 (Green Bay, Lake Michigan). Mixed stock analysis was conducted on 17 commercial harvest samples (n = 78–145/sample) collected from various ports lake-wide during 2009–2010. Results showed significant mixing with variability in stock composition across most samples. Samples consisted of two to four genetic stocks each accounting for ≥ 10% the catch. In 10 of 17 samples, the stock contributing the largest proportion made up < 60% of the harvest. In general, seasonal and annual differences existed in the proportional stock contribution at a single capture location. Samples from Wisconsin's primary commercial fishing management zone (WI-2) were composed predominately of fish from the Big Bay de Noc (Michigan) stock as opposed to the geographically proximate, North–Moonlight Bay (Wisconsin) stock. These findings have implications for management and allocation of fish to various quotas. Specifically, geographic location of harvest, the current means of allocating harvest quotas, is not the best predictor of genetic stock harvest.

Lake Michigan↗

Nonmigratory salmonids and tailwaters - a survey of stocking practices in the United States

A mail survey of fisheries agencies in the United States showed that 207.7 million nonmigratory salmonids were stocked in 1980 in the waters of 47 states (exclusive of the Great Lakes). Stocking in tailwaters accounted for 6.9 million or 3.3% of the total. In the South, 32.3% of all salmonids were stocked in tailwaters. Percentages stocked in tailwaters were lower in the West (1.8%), Midwest (1.5%), and Northeast (0.5%) because natural trout water is abundant in these regions. The rainbow trout ( Salmo gairdneri ) was the salmonid most commonly stocked in tailwaters, composing 95% of the fish 150 mm long or longer and 75% of the fish shorter than 150 mm. Nationally, tailwaters were more likely than other waters to be stocked with fish of the larger size.

Fisheries↗

Declining survival of lake trout stocked during 1963-1986 in U.S. waters of Lake Superior

The average catch per effort (CPE) values for the 1963&ndash;1982 year-classes of stocked lake trout Salvelinus namaycush caught at age 7 in gill nets and for the 1976&ndash;1986 year-classes caught at ages 2&ndash;4 in trawls declined significantly in U.S. waters of Lake Superior. The declines in CPE were not explained by reduced stocking, but rather by significant declines in survival indices of the year-classes of stocked lake trout. Increases in mortality occurred in year-classes before the fish reached ages 2&ndash;4, before they were recruited into the sport and commercial fisheries, and before they reached sizes vulnerable to sea lamprey predation. We conclude that declining abundance of stocked lake trout resulted from increased mortality, which may have been caused by competition, predation, or by a combination of these and other factors. Restoration of lake trout in Lake Superior may now depend on prudent management of naturally reproducing stocks rather than on stocking of hatchery-reared fish.

North American Journal of Fisheries Management↗

Development of an antimycin-impregnated bait for controlling common carp

The common carp Cyprinus carpio is a major problem for fisheries and wildlife managers because its feeding behavior causes degradation of valuable fish and waterfowl habitat. This study was designed to evaluate the effectiveness of an antimycin‐impregnated bait for control of common carp. The toxic bait contained fish meal, a binder, antimycin, and water. The ingredients were mixed together and made into pellets. This bait was force‐fed to common carp or administered in a pond environment, where fish voluntarily fed on the bait. The lowest lethal dose in the force‐feeding study was 0.346 mg antimycin/kg of fish and doses that exceeded 0.811 mg antimycin/kg were toxic to all fish. On three occasions, adult common carp held in 0.004‐ha concrete ponds were offered 10 g of toxic bait containing 5.0, 7.5, and 10 mg antimycin/g of bait and the mean mortalities 96 h later were 21, 35, and 51%, respectively. Three tests were conducted in 0.04‐ha earthen ponds each containing 100 adult common carp; these fish were offered 50 g of the toxic bait that contained 10 mg antimycin/g, and the mean mortalities (96 h) were 19, 32, and 74%. Toxic baits should be used in conjunction with other management techniques, and only when common carp are congregated and actively feeding, and when few nontarget bottom‐feeding species are present.

North American Journal of Fisheries Management↗

Site choice among Minnesota walleye anglers: The influence of resource conditions, regulations and catch orientation on Lake Preference

Understanding angler site choice preferences is important in the management of recreational fisheries to forecast angling demand and effort. This study investigated lake choice by recreational anglers fishing for walleye Sander vitreus in Minnesota and examined how choices were influenced by lake characteristics, angler demographics, and angler catch orientation. We collected data through a stated choice preference experiment using a survey administered to a sample of Minnesota resident ( n =1096) and nonresident ( n =535) anglers. Multinomial probit choice models were used to estimate preferences in lake choice. Lake characteristics included walleye abundance, walleye size, bag limit, slot limit, and distance from primary residence. Models included (1) lake characteristics only, (2) lake characteristics and angler demographics, and (3) lake characteristics with angler demographics and catch orientation factors. The coefficients of lake attributes had expected signs with greater preference for higher walleye abundance, larger walleye, bigger bag limits, absence of slot limits, and less driving time from home ( P <0.001 for all lake characteristics in the first model). Lake choice was influenced by the interaction of lake characteristics with age (negative with abundance of fish, P <0.100; positive with distance from home, P <0.001), metropolitan and out-of-state residency (positive with distance from home, P <0.001), and strength of preference for walleye (positive with distance, P <0.01). A stronger orientation to keep walleye was positively related to increased bag limits ( P <0.001) and negatively related to slot limits ( P <0.01). Study results have clear implications for managers—bag limits, relative to other lake characteristics, had a large influence on anglers’ lake choice for walleye fishing. Because of a stronger catch orientation among walleye anglers, low bag limits reduce lake preference. The results clarify the trade-offs that anglers make when selecting a place to fish for walleye and demonstrate how different management scenarios might influence angler participation.

Minnesota↗

The present status of the United States commercial fisheries of the Great Lakes

This review of the trends in production on the Great Lakes suggests that great biological changes have taken place. The general abundance of the choicer varieties, and of some of the less choice fishes, has been lowered considerably; and the prospects are that this level will fall still farther. In addition, the niches occupied by these finer species in the lakes have not been filled by coarser forms. Much of the reduced abundance in modern fishery must be attributed to overfishing or unwise fishing (cisco, whitefish, lake trout, chubs). Part of it we believe was caused by an infectious disease as was true for the smelt; part of it by the parasitic predator, the sea lamprey. Perhaps increased competition for space or food such as might have been brought about by the smelt in Lakes Huron and Michigan or the alewives in Lake Ontario may have played a role. Pollution, too, may have taken its toll. Often we have no better explanation to offer than to state that some unknown change in the environment was responsible.

Transactions of the North American Wildlife Confer↗