Adult Brook Trout Salvelinus Fontinalis Research Articles

Capture of Spawning Brook Trout by Electrofishing Does Not Impair Embryo Survival

AbstractElectrofishing is widely used to capture fish in freshwater systems. Fisheries assessment and fish culture activities that occur during spawning do so in the absence of a meaningful base of evidence about the potential effects of electrofishing on fish reproduction. In this laboratory experiment, we assessed whether electrofishing adult Brook Trout Salvelinus fontinalis affected the survival of their embryos. We used two genetically distinct strains of Brook Trout (domestic and wild‐origin strains) to do so. Both strains and sexes of fish were exposed to pulsed‐DC electrofishing techniques in a fully factorial design (i.e., male shocked, female shocked, both parents shocked, or neither parent shocked [control]), after which their incubating offspring were monitored for survival to the eyed egg, alevin, and fry stages. We did not detect any effects of our electrofishing treatment or interactions with the sex or strain of the fish exposed to electrofishing, suggesting that electrofishing did not negatively impact gamete viability. Our results support the use of responsible electrofishing to collect spawning salmonids for the purpose of gamete collection for hatchery rearing.

Variation in fish mercury concentrations in streams of the Adirondack region, New York: A simplified screening approach using chemical metrics

Simple screening approaches for the neurotoxicant methylmercury (MeHg) in aquatic ecosystems may be helpful in risk assessments of natural resources. We explored the development of such an approach in the Adirondack Mountains of New York, USA, a region with high levels of MeHg bioaccumulation. Thirty-six perennial streams broadly representative of 1st and 2nd order streams in the region were sampled during summer low flow and analyzed for several solutes and for Hg concentrations in fish. Several landscape and chemical metrics that are typically strongly related to MeHg concentrations in aquatic biota were explored for strength of association with fish Hg concentrations. Data analyses were based on site mean length-normalized and standardized Hg concentrations (assumed to be dominantly MeHg) in whole juvenile and adult Brook Trout Salvelinus fontinalis, Creek Chub Semotilus atromaculatus, Blacknose Dace Rhinichthys atratulus, and Central Mudminnow Umbra limi, as well as on multi-species z-scores. Surprisingly, none of the landscape metrics was related significantly to regional variation in fish Hg concentrations or to z-scores across the study streams. In contrast, several chemical metrics including dissolved organic carbon (DOC) concentrations, sulfate concentrations (SO42−), pH, ultra-violet absorbance (UV254), and specific ultra-violet absorbance were significantly related to regional variation in fish Hg concentrations. A cluster analysis based on DOC, SO42−, and pH identified three distinct groups of streams: (1) high DOC, acidic streams, (2) moderate DOC, slightly acidic streams, and (3) low DOC circum-neutral streams with relatively high SO42−. Preliminary analysis indicated no significant difference in fish Hg z-scores between the moderate and high DOC groups, so these were combined for further analysis. The resulting two groups showed strong differences (p<0.001) in DOC and SO42− concentrations as well as in pH and UV254 values. Median fish z-scores were significantly higher (p=0.002) in the group of streams with higher DOC and UV254 and lower pH and SO42−. Screening values of DOC >6.9mg/L, SO42− <2.8mg/L, pH <6.6, and UV254 >0.31cm−1 were tested as thresholds to identify Adirondack stream sites likely to have higher fish Hg concentrations. By applying a combined threshold of exceedance for either pH or UV254, sites with fish Hg concentrations that exceeded a wildlife guideline of 100ng/g were correctly identified about 75% of the time among the 36 study streams. An estimate of Hg risk applied to a data set of 391 streams based on DOC concentrations showed that about 28% were likely to pose high risk to wildlife; most of these streams were located in the western Adirondacks.

PH preference and avoidance responses of adult brook troutSalvelinus fontinalisand brown troutSalmo trutta

The pH preferred and avoided by wild, adult brook trout Salvelinus fontinalis and brown trout Salmo trutta was examined in a series a laboratory tests using gradual and steep-gradient flow-through aquaria. The results were compared with those published for the observed segregation patterns of juvenile S. fontinalis and S. trutta in Pennsylvania streams. The adult S. trutta tested showed a preference for pH 4·0 while adult S. fontinalis did not prefer any pH within the range tested. Salmo trutta are not found in Pennsylvania streams with a base-flow pH < 5·8 which suggests that S. trutta prefer pH well above 4·0. Adult S. trutta displayed a lack of avoidance at pH below 5·0, as also reported earlier for juveniles. The avoidance pH of wild, adult S. fontinalis (between pH 5·5 and 6·0) and S. trutta (between pH 6·5 and 7·0) did not differ appreciably from earlier study results for the avoidance pH of juvenile S. fontinalis and S. trutta. A comparison of c.i. around these avoidance estimates indicates that avoidance pH is similar among adult S. fontinalis and S. trutta in this study. The limited overlap of c.i. for avoidance pH values for the two species, however, suggests that some S. trutta will display avoidance at a higher pH when S. fontinalis will not. The results of this study indicate that segregation patterns of adult S. fontinalis and S. trutta in Pennsylvania streams could be related to pH and that competition with S. trutta could be mediating the occurrence of S. fontinalis at some pH levels.

Relationship between Electrofishing Catch Rate and Adult Trout Abundance in Wisconsin Streams

AbstractThe relative quickness and cost effectiveness of single‐pass electrofishing samples (catch per effort [CPE]) argues for their use over multiple‐pass estimates for enumerating stream fish populations. However, CPE can be an imprecise index of fish abundance and therefore may be less useful than more‐precise indices of abundance, such as those obtained from mark–recapture or depletion methods, for assessing trout populations. We evaluated the use of single‐pass electrofishing samples (catch/mi) as abundance (number/mi) predictors of adult brook trout Salvelinus fontinalis and brown trout Salmo trutta in Wisconsin streams by quantifying the relationship between electrofishing CPE and adult trout abundance. First, we tested for linearity of the relationship between CPE and adult trout abundance while accounting for measurement error. Next, we explained the residual variability in the relationship using physical and biological attributes of surveyed streams. We found that the relationship between CPE and adult trout abundance was proportional (linear) for both brook trout and brown trout. Electrofishing catchability did not differ significantly between trout species or among seasons or ecoregions. However, catchability was significantly greater for towed‐barge electrofishing (0.64; 95% confidence interval, 0.55–0.73) than backpack electrofishing (0.23; 0.09–0.59). Adult trout abundance alone explained 82% of the variation in CPE for backpack units and 87% of the variation in CPE for towed‐barge units. Stream habitat features such as stream slope, mean stream width, and pool density failed to explain additional variation in catchability. Our results indicate that CPE can provide a reliable index of adult trout abundance in Wisconsin streams, but mark–recapture methods may still be needed to obtain a more precise estimate of abundance. However, because time and effort can be reduced 50% if single‐pass CPEs are used instead of mark–recapture abundance estimates to predict adult trout abundance, managers may choose to sacrifice higher precision for reduced sampling effort.Received December 20, 2010; accepted June 17, 2011

Use of Outlet Barriers to Prevent Fall Emigration of Brook Trout Stocked in Adirondack Lakes

Outlet barriers in stocked lakes of the Adirondack Mountains were used to test the hypothesis that preventing fall emigration by adult brook trout Salvelinus fontinalis would increase trap-net and angling catch rates as well as the number of large trophy fish. Outlet barriers were maintained during the fall spawning season for 6 years on one lake and 10 years on another lake. We compared prebarrier and postbarrier trap-net and angler catches (1978–1998) in two blocked and two unblocked lakes. Postbarrier availability of brook trout to anglers and trap nets increased significantly in Rock Lake (blocked) but not in Lower Sylvan Pond (blocked) or the two unblocked lakes. However, highly significant increases in angler catches of trophy fish occurred from both blocked lakes. Variables other than emigration, such as number of fish stocked and angling mortality, influenced our ability to detect significant increases in the availability of age-2 and older brook trout in Lower Sylvan Pond. The outlet barriers elicited a population response by stocked brook trout consistent with the hypothesis that emigration losses of mature adults depleted older-aged fish from unblocked lakes. Outlet barriers are a potential management tool; however, managers must consider their specific management goals and the problems associated with seasonally interrupting migratory corridors.

Identification of Anadromous and Nonanadromous Adult Brook Trout and Their Progeny in the Tabusintac River, New Brunswick, by Means of Multiple-Stable-Isotope Analysis

Abstract Multiple-stable-isotope analysis was used to infer anadromous and nonanadromous origins of adult brook trout Salvelinus fontinalis and maternal migration history of age-0 progeny in the Tabusintac River, New Brunswick. Forty-seven adults collected above head of tide displayed deviations (δ) from standard ratios of 13C/12C, 15N/14N, and 34S/32S of −30.3‰ to −16.0‰, 7.4‰ to 16.8‰, and 1.5‰ to 14.1‰, respectively; higher values (positive or less negative) denote relatively greater enrichment in the heavier isotope. Isotopically enriched brook trout exhibited isotope profiles typical of fish from marine environments, and those that were isotopically depleted were considered to be of freshwater origin. Age-0 brook trout from Home Camp Pool, the most downstream freshwater rearing site sampled, were more enriched (δ13C = −24.4 ± 2.7‰ (mean ± SD), δ15N = 12.5 ± 3.1‰, and δ34S = 7.4 ± 1.8‰) than those at two other sites, and were believed to be progeny of anadromous females. Age-0 brook trout from the Bat...

A Multiple-Technique Approach to Investigating the Presumptive Low-Level Detection ofRenibacterium salmoninarumat a Broodstock Hatchery in Maine

Tissues from 160 fish were evaluated with a membrane filtration-fluorescent antibody technique (MF-FAT) and cultured with metabolite-supplemented media to determine if Renibacterium salmoninarum (Rs) or unrelated cross-reacting microorganisms were present in a population of hatchery-reared, adult brook trout Salvelinus fontinalis. Fluorescing bacteria were detected by the MF-FAT with fluorescein-labeled polyvalent antibody staining of kidney (8.8%), spleen (11.9%), and gut (13.1%); however, no Rs was confirmed by culture. Many fluorescing cells were morphologically consistent with Rs; others were not. Non-Rs bacteria, isolated by culture from three gut samples, reacted strongly by a direct fluorescent antibody test (DFAT) with polyvalent anti-Rs serum. Before this study began, a very low prevalence of fluorescing cells were detected in kidney smears by DFAT, and the hatchery was considered presumptively positive for Rs. We concluded from this study that systemic cross-reacting bacteria, detected in spleen and gut samples, could have contributed to previous questionable positive kidney smears. However, these cells did not account for all the fluorescing cells morphologically similar to Rs detected by MF-FAT. No tissue sample was confirmed Rs-positive by culture; therefore, the presumptive Rs-positive classification of the hatchery remains questionable. Even in the absence of definite results, this study illustrates a practical, multiple technique approach, with a combination of MF-FAT and metabolite-supplemented media, to evaluate fish populations suspected of low-level infections of Rs or in which cross-reacting bacteria are suspected of interfering with DFAT results.

Cadmium-Saturation Technique for Measuring Metallothionein in Brook Trout

Abstract A cadmium-saturation technique for quantifying metallothionein (MT) in mammalian tissues was evaluated for use in fish tissue. We administered 3 mg109 cadmium/kg body weight by intraperitoneal injection over a 5-d period to adult brook trout Salvelinus fontinalis to induce MT in liver and kidney tissues. The cadmium-saturation technique was modified so the amount of cadmium bound to unsaturated and cadmium-saturated MT could be measured. The method gave precise measurements of MT concentrations when aliquots of liver supernatant, which were analyzed separately, were quantified by atomic absorption or radiometric measurements. Two to four times more cadmium and MT concentrated in the liver of treated fish than in the kidney. Intraperitoneal administration of cadmium completely displaced copper and zinc from MT in liver of treated fish; cadmium concentrations in liver determined by the quantitation of cadmium-saturated MT and of unsaturated MT were identical. However, exposure of brook trout to cad...

Winter Stream Conditions and Use of Habitat by Brook Trout in High-Elevation Wyoming Streams

Abstract Winter stream conditions at elevations between 2,280 and 3,205 m above mean sea level and the use of winter habitat by adult brook trout Salvelinus fontinalis above 2,990 m were evaluated in 1983–1984 and 1984–1985. Little surface ice was observed at elevations above 2,900 m, which was associated with high snow accumulation; moderate surface ice and anchor ice formation were observed at elevations from 2,550 to 2,900 m; extensive surface ice formation occurred at 2,550 m. Little snow accumulated at 2,550 m and surface ice physically excluded substantial brook trout habitat. In late fall, brook trout at elevations above 2,990 m tended to move into low-gradient areas where they remained active throughout the winter. During winter, brook trout appeared to select for areas with maximum velocities of 15 cm/s or less, measured during summer low flow, and for deeper water, but not for substrate type.