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Maintaining intraspecific diversity is an important goal for fisheries conservation and recovery actions. While ecomorphological studies have demonstrated intraspecific diversity related to feeding or flow regime, there has been little assessment of such variation in regard to spawning habitat. We evaluated the relationship between individual morphology of Robust Redhorse and Notchlip Redhorse and variables describing the spawning habitat from which they were captured, such as current velocity, depth, and substrate particle size. Robust Redhorse (n = 58) and Notchlip Redhorse (n = 43) were captured from spawning aggregations in the lower Savannah River, South Carolina-Georgia using prepositioned grid electrofishers....
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Beam-based analytical methods are widely used to measure the concentrations of elements and isotopes in otoliths. These methods usually require that otoliths be individually mounted and prepared to properly expose the desired growth region to the analytical beam. Most analytical instruments, such as LA-ICPMS and ion and electron microprobes, have sample holders that will accept only one to six slides or mounts at a time. We describe a method of mounting otoliths that allows for easy transfer of many otoliths to a single mount after they have been prepared. Such an approach increases the number of otoliths that can be analyzed in a single session by reducing the need open the sample chamber to exchange slides-a particularly...
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We collected lake whitefish Coregonus clupeaformis off Alpena and Tawas City, Michigan, USA in Lake Huron and off Muskegon, Michigan USA in Lake Michigan during 2002–2004. We determined energy density and percent dry weight for lake whitefish from both lakes and lipid content for Lake Michigan fish. Energy density increased with increasing fish weight up to 800 g, and then remained relatively constant with further increases in fish weight. Energy density, adjusted for weight, was lower in Lake Huron than in Lake Michigan for both small (≤800 g) and large fish (>800 g). Energy density did not differ seasonally for small or large lake whitefish or between adult male and female fish. Energy density was strongly correlated...
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This paper describes the results of a field survey designed to test the prediction that the density of benthic juveniles of shallow-reef fishes is greater on wind-wave "exposed" sectors of a pair of isolated oceanic atolls (Kure, Pearl and Hermes) at the far northwestern end of the Hawaiian Islands, an archipelago in which east-northeasterly trade winds dominate onshore water flow and transport by surface currents. The densities of recruits (juveniles ???5 cm total length) were higher overall on windward versus leeward sectors of carbonate rock-rubble back reefs at both atolls, and the pattern was stronger for smaller (likely younger, more recently settled) recruits of four of the five most abundant species and...
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In the warming Arctic, aquatic habitats are in flux and salmon are exploring their options. Adult Pacific salmon, including sockeye (Oncorhynchus nerka), coho (O. kisutch), Chinook (O. tshawytscha), pink (O. gorbuscha) and chum (O. keta) have been captured throughout the Arctic. Pink and chum salmon are the most common species found in the Arctic today. These species are less dependent on freshwater habitats as juveniles and grow quickly in marine habitats. Putative spawning populations are rare in the North American Arctic and limited to pink salmon in drainages north of Point Hope, Alaska, chum salmon spawning rivers draining to the northwestern Beaufort Sea, and small populations of chum and pink salmon in Canada’s...
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Dramatic changes in seabird and marine mammal stocks in the Gulf of Alaska have been linked to shifts in abundance and composition of forage fish stocks over the past 20 years. The relative value (e.g., size and condition of individual fish, abundance) of specific forage fish stocks to predators under temporally changing oceanographic regimes is also expected to vary. We inferred potential temporal responses in abundance, growth, and age structure of a key forage fish, sand lance, by studying across spatially different oceanographic regimes. Marked meso-scale differences in abundance, growth, and mortality existed in conjunction with these differing regimes. Growth rate within stocks (between years) was positively...
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The imperiled status of sturgeons worldwide places priority on the identification and protection of critical habitats. We assessed the micro-structural and micro-chemical scope for a novel calcified structure, dorsal scutes, to be used for reconstruction of past habitat use and group separation in shortnose sturgeon (Acipenser brevirostrum). Dorsal scutes contained a dual-layered structure composed of a thin multi-layered translucent zone lying dorsally above a thicker multi-layered zone. Banding in the thick multi-layered zone correlated strongly with pectoral fin spine annuli supporting the presence of chronological structuring that could contain a chemical record of past environmental exposure. Trace element...
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This study compares simple fish communities of ten oligotrophic lakes in south-central Ontario. Species densities and population size structure vary significantly among these lake communities depending on fish species present beyond the littoral zone. Lake whitefish are fewer and larger in the presence of lake herring than in their absence. Diet analysis indicates that lake whitefish shift from feeding on both plankton and benthic prey when lake herring are absent to a primarily benthic feeding niche in the presence of lake herring. When benthic round whitefish are present, lake whitefish size and density decline and they move lower in the lake compared to round whitefish. Burbot are also fewer and larger in lakes...
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We evaluated cui-ui,Chasmistes cujus, swim-up success, time of hatching and swim-up, and size of larvae at swim-up under four fluctuating temperature regimes (8.9–15.0, 12.2–18.3, 15.0–21.1, and 17.8–23.9° C). The greatest swim-up success was at the 8.9–15.0° C regime and the lowest at the 15.0–21.1° C regime. Hatching and swim-up time varied inversely with incubation temperature. The largest (and presumably the most fit) larvae were in the 8.9–15.0° C treatment, whereas the smallest were in the 17.8–23.9° C treatment. Cui-ui appeared best adapted to the coolest of the four temperature regimes.
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We analyzed temporal changes in the dispersion of the rosyside dace,Clinostomus funduloides, (family Cyprinidae) in a headwater stream, to assess the role of habitat availability in promoting fish aggregation. The dace foraged alone and in groups of up to about 25 individuals, and dispersion varied significantly among monthly censuses conducted from May through December. In two of three study pools, dace aggregated during July, October and/or December, but spread out during other months, especially during September when dispersion did not differ significantly from random. Dispersion was not significantly correlated with the total amount of suitable habitat available to foraging dace, but during summer, corresponded...
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Stable 13C, 15N, and 34S isotopes were analyzed to define the feeding habitats of Acipenser oxyrinchus desotoi in the Suwannee and Yellow River populations. For the majority (93.9%) of Suwannee subadults and adults, 13C and 34S signatures indicate use of nearshore marine waters as primary winter feeding habitat, probably due to the limiting size of the Suwannee Sound estuary. In the Yellow River population, 13C isotope signatures indicate that adults remain primarily within Pensacola Bay estuary to feed in winter, rather than emigrating to the open Gulf of Mexico. A minor Suwannee River subset (6% of samples), comprised of juveniles and subadults, displayed 13C signatures indicating continued feeding in freshwater...
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In this laboratory study, we quantified substrate selection by small (<50 mm) and large (100-150 mm) ammocoetes of the least brook lamprey (Lampetra aepyptera). In aquaria, ammocoetes were given a choice to burrow into six equally-available substrate types: small gravel (2.360-4.750 mm), coarse sand (0.500-1.400 mm), fine sand (0.125-0.500 mm), organic substrate (approximately 70% decomposing leaves/stems and organic sediment particles, and 30% silt and fine sand), an even mixture of silt, clay, and fine sand, and silt/clay (<0.063 mm). Fine sand was selected with a significantly higher probability than any other substrate. Fine sand habitat is limited in many streams, in part owing to geology, but also as a result...
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We demonstrate the effectiveness of a genetic algorithm for discovering multi-locus combinations that provide accurate individual assignment decisions and estimates of mixture composition based on likelihood classification. Using simulated data representing different levels of inter-population differentiation (Fst ~ 0.01 and 0.10), genetic diversities (four or eight alleles per locus), and population sizes (20, 40, 100 individuals in baseline populations), we show that subsets of loci can be identified that provide comparable levels of accuracy in classification decisions relative to entire multi-locus data sets, where 5, 10, or 20 loci were considered. Microsatellite data sets from hatchery strains of lake trout,...
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Environmental conditions on higher latitude coral reefs can be extremely variable, and may structure fish communities in ways not previously observed in the more stable, low latitude locations where communities have usually been studied. Temporal changes in fish community structure were examined in an intensive two-year study of the reef fishes of Hanalei Bay, Kauai, Hawaii. Hanalei Bay is directly exposed to winter swells with high surf, as well as frequent heavy winter rainfall and high river discharge. Twenty-two transects (25 x 5 m) were established in a wide variety of habitats and censused monthly (N = 1052 censuses). Over 121 000 sightings of individuals from 150 species were made during the study. Seasonal...
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The physiological status of migrating steelhead kelts (Oncorhynchus mykiss) from the Situk River, Alaska, and two tributaries of the Clearwater River, Idaho, was evaluated to explore potential differences in post-spawning survival related to energy reserves. Blood plasma samples were analyzed for metrics related to nutritional and osmotic status, and samples of white muscle tissue collected from recent mortalities at weirs were analyzed for proximate constituents. Female kelts from the Situk River had significantly higher plasma cholesterol, triglycerides, glucose and calcium concentrations, all of which suggested higher lipid and energy stores. Additional support for energy limitation in kelts was provided by evaluating...
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Worldwide, streams and rivers are facing a suite of pressures that alter water quality and degrade physical habitat, both of which can lead to changes in the composition and richness of fish populations. These potential changes are of particular importance in the Southeast USA, home to one of the richest stream fish assemblages in North America. Using data from 83 stream sites in North Carolina sampled in the 1960’s and the past decade, we used hierarchical Bayesian models to evaluate relationships between species richness and catchment land use and land cover (e.g., agriculture and forest cover). In addition, we examined how the rate of change in species richness over 50 years was related to catchment land use...
Using a variety of sampling techniques and observations we describe aspects of the reproductive ecology and early life-history of Bear Lake sculpin, Cottus extensus, a species endemic to Bear Lake, Utah-Idaho. Adult sculpin spawned in shallow water (0.5-6.0 m depths) in cavities beneath large cobbles and boulders. During 1993, egg mass densities were highest (> 4.0 m(2)) at 1.0-2.0 m depths. Electivity indices verified substrate selection and also indicated an avoidance of sand- and gravel-embedded materials. During years of low water elevation, suitable spawning substrates were restricted to one Or two limited areas of the lake and comprised < 0.004% of the total benthic area. Disturbance from turbulence, as would...


map background search result map search result map Adaptive strategies and life history characteristics in a warming climate: salmon in the Arctic? Adaptive strategies and life history characteristics in a warming climate: salmon in the Arctic?