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USGS2011

Approximate sample sizes required to estimate length distributions

The sample sizes required to estimate fish length were determined by bootstrapping from reference length distributions. Depending on population characteristics and species-specific maximum lengths, 1-cm length-frequency histograms required 375-1,200 fish to estimate within 10% with 80% confidence, 2.5-cm histograms required 150-425 fish, proportional stock density required 75-140 fish, and mean length required 75-160 fish. In general, smaller species, smaller populations, populations with higher mortality, and simpler length statistics required fewer samples. Indices that require low sample sizes may be suitable for monitoring population status, and when large changes in length are evident, additional sampling effort may be allocated to more precisely define length status with more informative estimators. ?? Copyright by the American Fisheries Society 2007.

Transactions of the American Fisheries Society↗
USGS2011

Effects of turbidity, light level, and cover on predation of white sturgeon larvae by prickly sculpins

White sturgeon Acipenser transmontanus occur in rivers of the western United States and southwestern Canada, but some populations are in decline because of recruitment failure. Many river systems in this area have been altered as a result of development that has caused major environmental changes. Our goal was to examine how three changes - lower turbidity levels, higher light levels, and altered substrates - might affect predation by prickly sculpin Cottus asper on white sturgeon larvae. We experimentally investigated predation at various turbidity levels and found that significantly more white sturgeon yolk sac larvae were eaten at lower turbidity levels. The effects of light level (1-4 and 7-15 1x), the presence or absence of rocks as cover, and prey size (14-17 mm and 20-24 mm total length) on the outcome of predator-prey interactions were also examined. Significantly fewer white sturgeon were eaten during trials that combined the lowest light level, cover, and the smallest larvae. Our results suggest that altered river conditions caused by impoundment and other factors have increased predation on white sturgeon larvae. ?? Copyright by the American Fisheries Society 2005.

Transactions of the American Fisheries Society↗
USGS2011

Development of a bioenergetics model for humpback chub and evaluation of water temperature changes in the Grand Canyon, Colorado River

The construction of Glen Canyon Dam above the Grand Canyon (Arizona) has reduced the water temperature in the Colorado River and altered the growth rate and feeding patterns of the federally endangered humpback chub Gila cypha. A bioenergetics model for humpback chub was developed and used to examine how warmer water temperatures in the lower Colorado River (achieved through a temperature control device [TCD] at Glen Canyon Dam) might influence their growth rate and food requirements. Parameter values for humpback chub were developed by Monte Carlo filtering and fitting to laboratory growth. Parameter bounds were established from the literature for Gila species, random parameter sets were selected within these bounds, and the growth of modeled humpback chub was compared with criteria from a laboratory growth experiment at 24??C. This method of parameter estimation could be applied to other imperiled fishes where physiological studies are impractical. Final parameter values were corroborated by comparison with the growth rates of humpback chub from independent field and laboratory studies. Simulations indicated that increasing water temperatures from approximately 9??C to 16??C during summer and fall, the change expected from the TCD, may have a minimal effect on humpback chub growth rate unless food availability also increases with temperature. To evaluate the effects of increased temperatures on humpback chub in the lower Colorado River, it will be essential to monitor their growth rate, the invertebrate community, and the predators of humpback chub, which are also influenced by temperature changes. Bioenergetics models for humpback chub and their predators should be helpful tools for identifying potential scenarios and evaluating the complex interactions resulting from a TCD. ?? Copyright by the American Fisheries Society 2005.

Transactions of the American Fisheries Society↗
USGS2011

Influence of landscape-scale factors in limiting brook trout populations in Pennsylvania streams

Landscapes influence the capacity of streams to produce trout through their effect on water chemistry and other factors at the reach scale. Trout abundance also fluctuates over time; thus, to thoroughly understand how spatial factors at landscape scales affect trout populations, one must assess the changes in populations over time to provide a context for interpreting the importance of spatial factors. We used data from the Pennsylvania Fish and Boat Commission's fisheries management database to investigate spatial factors that affect the capacity of streams to support brook trout Salvelinus fontinalis and to provide models useful for their management. We assessed the relative importance of spatial and temporal variation by calculating variance components and comparing relative standard errors for spatial and temporal variation. We used binary logistic regression to predict the presence of harvestable-length brook trout and multiple linear regression to assess the mechanistic links between landscapes and trout populations and to predict population density. The variance in trout density among streams was equal to or greater than the temporal variation for several streams, indicating that differences among sites affect population density. Logistic regression models correctly predicted the absence of harvestable-length brook trout in 60% of validation samples. The r 2-value for the linear regression model predicting density was 0.3, indicating low predictive ability. Both logistic and linear regression models supported buffering capacity against acid episodes as an important mechanistic link between landscapes and trout populations. Although our models fail to predict trout densities precisely, their success at elucidating the mechanistic links between landscapes and trout populations, in concert with the importance of spatial variation, increases our understanding of factors affecting brook trout abundance and will help managers and private groups to protect and enhance populations of wild brook trout. ?? Copyright by the American Fisheries Society 2006.

Transactions of the American Fisheries Society↗
USGS2011

Spawning distribution of sockeye salmon in a glacially influenced watershed: The importance of glacial habitats

The spawning distribution of sockeye salmon Oncorhynchus nerka was compared between clear and glacially turbid habitats in Lake Clark, Alaska, with the use of radiotelemetry. Tracking of 241 adult sockeye salmon to 27 spawning locations revealed both essential habitats and the relationship between spawn timing and seasonal turbidity cycles. Sixty-six percent of radio-tagged sockeye salmon spawned in turbid waters (???5 nephelometric turbidity units) where visual observation was difficult. Spawning in turbid habitats coincided with seasonal temperature declines and associated declines in turbidity and suspended sediment concentration. Because spawn timing is heritable and influenced by temperature, the observed behavior suggests an adaptive response to glacier-fed habitats, as it would reduce embryonic exposure to the adverse effects of fine sediments. ?? Copyright by the American Fisheries Society 2007.

Transactions of the American Fisheries Society↗
USGS2011

Previously undocumented two-year freshwater residency of juvenile coho salmon in Prairie Creek, California

Over 2,000 juvenile coho salmon Oncorhynchus kisutch were tagged with passive integrated transponder (PIT) tags during the fall of 1998 and 1999 in Prairie Creek, California, as part of a study on individual winter growth rates and movement of juvenile coho salmon. During this study, age-2 out-migrants were incidentally observed. Previously, it had been generally assumed that all juvenile coho salmon in northern California streams spend only 1 year in freshwater before out-migrating at age 1 and that a 2-year freshwater life history pattern was found only in the more northerly portions of the species' range. Subsequently, scale analysis of PIT-tagged fish recaptured during spring out-migration was used as a basis for estimating the proportion of out-migrants displaying a 1- or 2-year freshwater residency life history. Twenty-eight percent (28%) of out-migrants captured in spring 2000 displayed a 2-year freshwater residency life history, apparently related to low winter growth rates documented in related research in the study stream. ?? Copyright by the American Fisheries Society 2007.

Transactions of the American Fisheries Society↗
USGS2011

Phylogenetic and ecological characteristics associated with thiaminase activity in Laurentian Great Lakes fishes

Thiamine deficiency complex (TDC) causes mortality and sublethal effects in Great Lakes salmonines and results from low concentrations of egg thiamine that are thought to be caused by thiaminolytic enzymes (i.e., thiaminase) present in the diet. This complex has the potential to undermine efforts to restore lake trout Salvelinus namaycush and severely restrict salmonid production in the Great Lakes. Although thiaminase has been found in a variety of Great Lakes fishes, the ultimate source of thiaminase in Great Lakes fishes is currently unknown. We used logistic regression analysis to investigate relationships between thiaminase activity and phylogenetic or ecological characteristics of 39 Great Lakes fish species. The taxonomically more ancestral species were more likely to show thiaminase activity than the more derived species. Species that feed at lower trophic levels and occupy benthic habitats also appeared to be more likely to show thiaminase activity; these variables were correlated with taxonomy, which was the most important predictor of thiaminase activity. Further analyses of the relationship between quantitative measures of thiaminase activity and ecological characteristics of Great Lakes fish species would provide greater insight into potential sources and pathways of thiaminase in Great Lakes food webs. ?? Copyright by the American Fisheries Society 2008.

Transactions of the American Fisheries Society↗
USGS2011

Seasonal distribution, aggregation, and habitat selection of common carp in Clear Lake, Iowa

The common carp Cyprinus carpio is widely distributed and frequently considered a nuisance species outside its native range. Common carp are abundant in Clear Lake, Iowa, where their presence is both a symptom of degradation and an impediment to improving water quality and the sport fishery. We used radiotelemetry to quantify seasonal distribution, aggregation, and habitat selection of adult and subadult common carp in Clear Lake during 2005-2006 in an effort to guide future control strategies. Over a 22-month period, we recorded 1,951 locations of 54 adults and 60 subadults implanted with radio transmitters. Adults demonstrated a clear tendency to aggregate in an offshore area during the late fall and winter and in shallow, vegetated areas before and during spring spawning. Late-fall and winter aggregations were estimated to include a larger percentage of the tracked adults than spring aggregations. Subadults aggregated in shallow, vegetated areas during the spring and early summer. Our study, when considered in combination with previous research, suggests repeatable patterns of distribution, aggregation, and habitat selection that should facilitate common carp reduction programs in Clear Lake and similar systems. ?? Copyright by the American Fisheries Society 2008.

Transactions of the American Fisheries Society↗
USGS1947

Mortality of smelt, Osmerus mordax (Mitchill), in Lakes Huron and Michigan during the fall and winter of 1942-1943

The mortality that nearly exterminated the huge stocks of smelt in Lakes Huron and Michigan during the fall and winter of 1942–1943 appears to have originated in central Lake Huron in the Saginaw Bay area in late September or early October 1942. The mortality spread rapidly northward reaching the Drummond Island area about the latter part of October and the St. Ignace region of the Straits of Mackinac near the end of the month. In the latter part of October smelt died also in the Canadian waters of Lake Huron including North Channel and Georgian Bay but exact details as to time and course are lacking. There is some evidence that the epidemic had not reached the Ontario shore of central Lake Huron by late May 1943. Spreading through northern Lake Michigan the mortality had penetrated as far south as Grand Traverse Bay by November 19 and as far west as Point Aux Barques, Michigan, by November 26, 1942. Smelt were reported to be dying in Lake Charlevoix, Michigan, in early February 1943, and in Green Bay toward the middle of that month. The mortality did not reach Crystal Lake where in contrast to Lake Charlevoix a dam barred the passage of fish from Lake Michigan. At the time of the 1943 spring spawning run (April) only a few scattered survivors remained from the vast populations. After consideration of possible causes, it was concluded that the mortality could be explained only as resulting from a communicable disease (bacteria or virus). This explanation alone is in harmony with the following facts: the mortality was progressive, spreading from one area into adjacent areas over a period of at least 4 1/2 months and under a great diversity of habitat conditions; only smelt were affected but within the species death overtook fish of all sizes from 2 inches on and all ages of both sexes, mature and immature; the mortality penetrated Lake Charlevoix where the passage of fish to and from Lake Michigan was possible but did not reach Crystal Lake where the passage from Lake Michigan was barred by a dam; the epidemic did not reach other inland lakes where free and easy access from the Great Lakes was impossible nor did it extend to Lakes Superior, Erie, and Ontario. Considered at first as a nuisance and a threat to the native fishes of the Great Lakes, the smelt ultimately became a fish of primary importance to commercial fishermen, sportsmen, and others. In Green Bay, the center of the commercial fishery, smelt became the dominant commercial species, yielding more than 4 million pounds in some years. Almost all of the commercial production was from nets set under the ice. The take by amateurs and others who dipped smelt from streams during the spawning run was even greater, amounting to as much as 5 1/2 million pounds in a single year in the State of Michigan alone (the yield in Wisconsin may have been nearly as great). The mortality of smelt was a severe blow to the nation's war-time food-production program. It is estimated that in 1943, in which year elaborate preparations had been made for the efficient utilization of the spawning-run production, the mortality reduced the output of smelt by about 13 million pounds. The total loss through the present (1946) season can be set in the neighborhood of 50 million pounds. The first indication of a recovery of the smelt came in 1945 when a small amount was produced commercially in Green Bay and numerous light runs occurred in streams tributary to Lakes Huron and Michigan. The general level of abundance in 1945, however, is believed to have been less than 10 per cent of that of “pre-mortality” years. Such information as is available for 1946 suggests considerable further improvement in this year. Given good survival of young, it is anticipated that a large rise in the abundance of smelt can occur in 1947 and that by 1948 or 1949 the size of the populations should no longer be influenced by the number of spawners available in preceding years. The smelt from the Escanaba area of Green Bay were without exception significantly longer and heavier in 1944 and 1945 than were fish of corresponding age captured in the same region in 1941. Furthermore, three of four comparisons indicated significantly greater size in 1945 than in 1944. This improvement in growth rate is believed to have been associated with the reduction in the smelt population brought about by the 1942–1943 mortality.

Transactions of the American Fisheries Society↗
USGS1999

Fire and aquatic ecosystems in forested biomes of North America

Synthesis of the literature suggests that physical, chemical, and biological elements of a watershed interact with long‐term climate to influence fire regime, and that these factors, in concordance with the postfire vegetation mosaic, combine with local‐scale weather to govern the trajectory and magnitude of change following a fire event. Perturbation associated with hydrological processes is probably the primary factor influencing postfire persistence of fishes, benthic macroinvertebrates, and diatoms in fluvial systems. It is apparent that salmonids have evolved strategies to survive perturbations occurring at the frequency of wildland fires (10°–10 2 years), but local populations of a species may be more ephemeral. Habitat alteration probably has the greatest impact on individual organisms and local populations that are the least mobile, and reinvasion will be most rapid by aquatic organisms with high mobility. It is becoming increasingly apparent that during the past century fire suppression has altered fire regimes in some vegetation types, and consequently, the probability of large stand‐replacing fires has increased in those areas. Current evidence suggests, however, that even in the case of extensive high‐severity fires, local extirpation of fishes is patchy, and recolonization is rapid. Lasting detrimental effects on fish populations have been limited to areas where native populations have declined and become increasingly isolated because of anthropogenic activities. A strategy of protecting robust aquatic communities and restoring aquatic habitat structure and life history complexity in degraded areas may be the most effective means for insuring the persistence of native biota where the probability of large‐scale fires has increased.

Transactions of the American Fisheries Society↗
USGS2011

Migration and spawning of radio-tagged zulega Prochilodus argenteus in a dammed Brazilian river

It is difficult for agencies to evaluate the impacts of the many planned dams on Sa??o Francisco River, Brazil, migratory fishes because fish migrations are poorly known. We conducted a study on zulega Prochilodus argenteus, an important commercial and recreational fish in the Sa??o Francisco River, to identify migrations and spawning areas and to determine linear home range. During two spawning seasons (2001-2003), we radio-tagged fish in three main-stem reaches downstream of Tre??s Marias Dam (TMD), located at river kilometer (rkm) 2,109. We tagged 10 fish at Tre??s Marias (TM), which is 5 km downstream of TMD; 12 fish at Pontal, which is 28 km downstream of TMD and which includes the mouth of the Abaete?? River, and 10 fish at Cilga, which is 45 km downstream of TMD. Late-stage (ripe) adults tagged in each area during the spawning season remained at or near the tagging site, except for four Cilga fish that went to Pontal and probably spawned. The Pontal area at the Abaete?? River mouth was the most important spawning site we found. Prespawning fish moved back and forth between main-stem staging areas upstream of the Abaete?? River mouth and Pontal for short visits. These multiple visits were probably needed as ripe fish waited for spawning cues from a flooding Abaete?? River. Some fish homed to prespaw ning staging areas, spawning areas, and nonspawning areas. The migratory style of zulega was dualistic, with resident and migratory fish. Total linear home range was also dualistic, with small (<26-km) and large (53-127-km) ranges. The locations of spawning areas and home ranges suggest that the Pontal group (which includes Cilga fish) is one population that occupies about 110 km. The Pontal population overlaps a short distance with a population located downstream of Cilga. Movements of late-stage TM adults suggest that the TM group is a separate population, possibly with connections to populations upstream of TMD. ?? Copyright by the American Fisheries Society 2006.

Transactions of the American Fisheries Society↗
USGS2011

Seasonal and diel movements and habitat use of robust redhorses in the Lower Savannah River, Georgia and South Carolina

The robust redhorse Moxostoma robustum is a large riverine catostomid whose distribution is restricted to three Atlantic Slope drainages. Once presumed extinct, this species was rediscovered in 1991. Despite being the focus of conservation and recovery efforts, the robust redhorse's movements and habitat use are virtually unknown. We surgically implanted pulse-coded radio transmitters into 17 wild adults (460-690 mm total length) below the downstream-most dam on the Savannah River and into 2 fish above this dam. Individuals were located every 2 weeks from June 2002 to September 2003 and monthly thereafter to May 2005. Additionally, we located 5-10 individuals every 2 h over a 48-h period during each season. Study fish moved at least 24.7 ?? 8.4 river kilometers (rkm; mean ?? SE) per season. This movement was generally downstream except during spring. Some individuals moved downstream by as much as 195 rkm from their release sites. Seasonal migrations were correlated to seasonal changes in water temperature. Robust redhorses initiated spring upstream migrations when water temperature reached approximately 12??C. Our diel tracking suggests that robust redhorses occupy small reaches of river (???1.0 rkm) and are mainly active diurnally. Robust redhorses were consistently found in association with woody debris and gravel streambed sediments along the outer edge of river bends. Fish exhibited a high degree of fidelity to both overwintering and spawning areas. Our observations of long-distance seasonal migrations suggest that successful robust redhorse conservation efforts may require an ecosystem management approach. ?? Copyright by the American Fisheries Society 2006.

Transactions of the American Fisheries Society↗
USGS2011

Diel behavior of adult striped bass using tailwater habitat as summer refuge

General patterns of summer diel distribution and movement were identified for adult striped bass Morone saxatilis using tailwater habitat influenced by the diel operation cycle of a hydroelectric dam during the summers of 2003 and 2004. Striped bass distribution within the tailwater was similar during each diel-tracking event and across both summers. The majority of fish remained within the tailwater the entire summer; however, some made periodic excursions to and from the tailwater throughout the summer. Further, most striped bass were located within 0.5 km of Richard B. Russell Dam during all stages of operation on all occasions - probably because of the constant availability of optimal habitat during all three stages of operation on all diel-tracking events. The diel cycle of dam operation, which included pumped storage during each summer, did not degrade tailwater habitat below optimal conditions, according to summer habitat suitability index values for inland adult striped bass. Movement was significantly higher during hydroelectric generation operations than during no-generation and pumped storage periods in summer 2003; this difference was not apparent during summer 2004. Mean absolute movement peaked during hydroelectric generation on six of eight diel-tracking events. During both summers, movement was directed up-reservoir during no-generation and generation periods and down-reservoir during pumped storage. Mean total daily movement rates ranged from 0.59 to 4.04 km/d and were greater than those previously estimated from bimonthly sampling for this population. Total daily movement rate peaked during the first tracking event each summer and then declined as summer progressed. These findings suggest that hydroelectric discharges affect adult striped bass behavior, but the effects are not adverse as long as habitat is not degraded by hydroelectric facility operations. ?? Copyright by the American Fisheries Society 2007.

Transactions of the American Fisheries Society↗
USGS2011

Influence of gravel mining and other factors on detection probabilities of Coastal Plain fishes in the Mobile River Basin, Alabama

We used an information-theoretic approach to examine the variation in detection probabilities for 87 Piedmont and Coastal Plain fishes in relation to instream gravel mining in four Alabama streams of the Mobile River drainage. Biotic and abiotic variables were also included in candidate models. Detection probabilities were heterogeneous across species and varied with habitat type, stream, season, and water quality. Instream gravel mining influenced the variation in detection probabilities for 38% of the species collected, probably because it led to habitat loss and increased sedimentation. Higher detection probabilities were apparent at unmined sites than at mined sites for 78% of the species for which gravel mining was shown to influence detection probabilities, indicating potential negative impacts to these species. Physical and chemical attributes also explained the variation in detection probabilities for many species. These results indicate that anthropogenic impacts can affect detection probabilities for fishes, and such variation should be considered when developing monitoring programs or routine sampling protocols. ?? Copyright by the American Fisheries Society 2008.

Transactions of the American Fisheries Society↗
USGS1999

Biomass of coastal cutthroat trout in unlogged and previously clearcut basins in the central Coast Range of Oregon

Populations of coastal cutthroat trout Oncorhynchus clarki clarki were sampled in 16 Oregon headwater streams during 1991–1993. These streams were above upstream migration barriers and distributed among basins that had been logged 20–30 and 40–60 years ago and basins that had not been logged but had burned 125–150 years ago. The objective of our study was to characterize the populations and habitats of age-1 or older cutthroat trout within these three forest management types. Streams within unlogged basins had relatively low levels and a small range of trout biomass (g/m 2 ). Streams in basins logged 40–60 years ago supported low levels but an intermediate range of trout biomass. Streams in basins logged 20–30 years ago supported the widest range of biomass, including the lowest and highest biomasses among all streams sampled. The variable that best explained the variation of trout biomass among all 16 streams was the amount of large woody debris (LWD). All streams were heavily shaded during at least part of the year by mostly closed tree canopies. Deciduous trees were more prominent in canopies over streams in logged basins, while conifers were more prominent in the stream canopies of unlogged basins. Our results suggest that trout production in basins extensively clear-cut 20–60 years ago may generally decrease or remain low over the next 50 or more years because of decreasing loads of remnant LWD, persistent low recruitment potential for new LWD, and persistent heavy shading by conifers. These logged basins are not likely to show an increase in trout biomass over the next 50 years unless reset by favorable natural disturbances or by habitat restoration efforts.

Oregon↗