Jerre W. Mohler

Producing Fluorescent Marks on Atlantic Salmon Fin Rays and Scales with Calcein via Osmotic Induction

Abstract Calcified tissues of Atlantic salmon in both larval and postscale developmental life stages became labeled with the fluorochrome dye known as calcein in 7 min by sequential immersion in salt and calcein solutions. I introduce the term “osmotic induction” to describe this process. At 47 d posttreatment, fish that had been exposed to osmotic induction of calcein as nonfeeding larvae exhibited mortality and growth equivalent to that of nonexposed fish (P < 0.05). Atlantic salmon parr (at 5 months posthatch) exposed to osmotic induction of calcein exhibited no mortality during a 120-d posttreatment period. In addition to inducing a calcein mark on fin rays of all larvae and parr, the procedure also produced a distinct calcein mark on scales of parr. A second exposure of parr to osmotic induction 90 d after the first produced a conspicuous 2-band pattern on scales which corresponded to the two separate marking events. Calcein marks are invisible to the unaided eye but were observed without sacrificing...

MANAGEMENT BRIEFS Immersion of Larval Atlantic Salmon in Calcein Solutions to Induce a Non-Lethally Detectable Mark

Abstract At 60 d posthatch. larval Atlantic salmon Salmo salar were immersed in water containing calcein at 125 or 250 mg/L or oxytetracycline at 250 mg/L or in untreated control water. Immersions were static, 48-h treatments. All fish immersed in calcein solutions acquired a chemical mark visible microscopically under long-wave ultraviolet light and manifested as apple-green fluorescence in calcified structures, including fin rays. No fluorescence was detected in fish immersed in oxytetracycline or untreated water when viewed in the same manner. Mortality from the time of immersion through day 10 was significantly higher (P ≤ 0.05) in 250 mg calcein/L (10.5%) than in 125 mg calcein/L (< 1.0%). At 234 d postimmersion, the calcein mark was detected non-lethally in samples of caudal fin tissue from over 93% of calcein-treated fish examined. Results suggest that calcein may be a valuable tool for mass-marking larval fish for long-term hatchery product evaluation.

Growth and Survival of First-Feeding and Fingerling Atlantic Sturgeon under Culture Conditions

Abstract We performed rearing studies with first-feeding fry and fingerling Atlantic sturgeon Acipenser oxyrinchus oxyrinchus produced from streamside spawning of wild Hudson River adults. In all, 20,000 larvae were reared in 54-L circular tanks at initial densities of 3.7–29.6 fish/L (0.06–0.52 g/L). At the onset of exogenous feeding, diet treatments included live brine shrimp Artemia sp., frozen brine shrimp, or commercially formulated Biokyowa B-250. At the end of the 26-d study, all treatments but two had survival greater than 93%. Mean specific growth rate (SGR) was inversely proportional to fish density. Fish fed frozen brine shrimp were smaller but had equivalent survival to those fed live brine shrimp. Atlantic sturgeon converted to formulated feed with less than 25% mortality at mean total length and weight of 34.5 mm and 0.18 g in 20–26 d at initial stocking densities of 7.4 fish/L or less. A subsequent study was performed with fingerlings at densities of 0.37–2.22 g/L. These fingerlings were of...

Communications: Feeding Trials with Juvenile Atlantic Sturgeons Propagated from Wild Broodstock

Abstract Juvenile Atlantic sturgeons Acipenser oxyrinchus produced by hormone-induced spawning of wild broodstock from the Hudson River, New York, were used in a diet study. Fish fed live Artemia sp. as first-feeding fry for 35 d were observed to convert readily to formulated diets. At 79 d posthatch, four formulated feeds were offered: sturgeon starter 9304, Biokyowa, Zeigler esocid diet, and Tunison sturgeon starter. At the end of 60 d, fish fed Biokyowa had the greatest growth and best feed conversion (P ≤ 0.05). Feed conversions were significantly different between all treatments, indicating wide variability in growth response to the diets tested. Proximate analyses of diets showed Biokyowa highest in protein (59.43%) and dry matter (97.28%).

Dietary Calcein Marking of Brook Trout, Atlantic Salmon, Yellow Perch, and Coho Salmon Scales

Abstract Brook trout Salvelinus fontinalis, Atlantic salmon Salmo salar, coho salmon Oncorhynchus kisutch, and yellow perch Perca flavescens fed calcein for 5 d showed characteristic calcein scale marks 7–10 d postmarking. In fish fed 0.75 or 1.25 g of calcein per kilogram of feed, the percentage of fish that exhibited a calcein mark was 100% in brook trout, 93–98% in Atlantic salmon, 60% in yellow perch, and 0% in coho salmon. However, when coho salmon were fed 5.25 g calcein/kg feed, 100% marking was observed 7–10 d postmarking. Brook trout were successfully marked twice with distinct bands when fed calcein 5 months apart. Brook trout scale pixel luminosity increased as dietary calcein increased in experiment 2. For the second calcein mark, scale pixel luminosity from brook trout fed 1.25 g calcein/kg feed was numerically higher (P < 0.08) than scales from fish fed 0.75 g calcein/kg feed. Mean pixel luminosity of calcein-marked Atlantic salmon scales was 57.7 for fish fed 0.75 g calcein/kg feed and 55.2...

Effect of Artificial Sunlight on the Retention of External Calcein Marks on Lake Trout

Abstract When choosing a fish marking technique to address fishery related questions, it is important to consider factors that affect mark retention. Calcein, a chemical marking agent, is under investigation for potential use on fish. Two laboratory trials were conducted with calcein-marked lake trout Salvelinus namaycush to determine the effect of artificial sunlight on calcein mark intensity. In trial 1, fish exposed to 18,000 lx for 7 d lost 90% or more of the calcein mark intensity (relative to the colorimetric key, mg/L) on the head, body, ventral region, and pectoral fins relative to mark intensity in fish that were maintained in darkness. In trial 2, light intensity was reduced 2.5–3.0-fold. After 7 d of light exposure, calcein mark intensity on the head was reduced by 40–45% relative to mark intensity in fish that were held in darkness; by day 14, calcein mark intensity on the head was reduced by 55–60% relative to that of dark-treated fish. No further decline was observed in light-exposed fish, a...

Predation by Captive Wild Brook Trout on Calcein-Marked versus Nonmarked Atlantic Salmon Fry

Abstract Juvenile Atlantic salmon Salmo salar and other fish species marked with the fluorochrome dye calcein exhibit a green fluorescence in fin rays and other calcified structures under specific optical conditions. To determine whether brook trout Salvelinus fontinalis would preferentially prey upon calcein-marked individuals, we introduced calcein-marked and nonmarked Atlantic salmon fry simultaneously to captive wild brook trout in four controlled indoor raceway trials. Each trial consisted of 2 brook trout and 100 each of calcein-marked and nonmarked Atlantic salmon fry; no individuals were used in more than one trial. At the termination of each 3-d trial, predators were removed from raceways, and surviving Atlantic salmon fry were examined with a calcein detection device to tally numbers of marked and nonmarked individuals. In individual trials, 2 brook trout consumed between 20 and 99 Atlantic salmon fry over a 3-d period (10–49% of available prey). Replicated goodness-of-fit (G-statistic) analysis...

The Effect of Rearing Density on Growth, Survival, and Feed Conversion of Juvenile Atlantic Sturgeon

Abstract We investigated the effect of rearing density on the growth and survival of juvenile Atlantic sturgeon Acipenser oxyrinchus using initial rearing densities ranging from 10 to 30 fish per tank or 3.6–10.9 kg/m2 of substrate. The mean weight of fish at the start of the trial was 368.7 g. After 7 weeks of rearing, density ranged from 6.5 to 16.3 kg/m2 (14.7–36.6 g/L). Fish reared at the lowest density had significantly higher mean weight and length at the end of the trial. Growth over the 7-week experiment was modeled as a function of time, and growth rate was inversely proportional to density. The mean increase in total biomass was 63.14%, and the mean daily length gain was 0.23%. Overall survival was 99.7%, and calculated feed conversion rates ranged from 1.93 to 2.65. However, feed conversion rates were likely not at maximum levels due to the selection of a relatively high experimental feeding rate (2.5% of body weight per day).

The Mussels of Muddy Creek on Erie National Wildlife Refuge

Abstract A qualitative mussel survey was performed on Muddy Creek, a tributary to French Creek in Crawford County, PA, within the boundaries of the Erie National Wildlife Refuge. Riffle-run-pool sequences were sampled at 20 locations in the study area using visual and tactile timed-search techniques. Live specimens represented by 22 species were encountered at a rate of 54 individuals per person-hour and included the federally-endangered Pleurobema clava (clubshell) and Epioblasma torulosa rangiana (northern riffleshell) as well as four Pennsylvania state-imperiled species. Evidence of recruitment in the clubshell population was found in excavated quadrats and by hand-collecting. Brillouin diversity indices ranged from 0.35–2.88 over the study area, with a mean (SD) of 1.67 (0.59). The three most abundant species were Actinonaias ligamentina, Amblema plicata, and Lasmigona costata, while the three most rare were Anodontoides ferussacianus, E. torulosa rangiana, and Villosa fabalis. The high diversity of mussels along with the presence of federally listed and state-imperiled species warrants a pro-active approach to future protection of the aquatic resources of Muddy Creek.

Quality Assessment of Wild Atlantic Sturgeon Semen under Conditions of Short-Term Storage

Abstract Short-term storage trials were conducted with semen of Atlantic sturgeon Acipenser oxyrinchus collected from a total of nine wild males during the 2008 and 2009 spawning seasons on the Hudson River. Semen samples were kept refrigerated (4 ± 1°C) and stored in different gaseous atmospheres and storage extenders. The gaseous environments included oxygen, nitrogen, and air, while the extender treatments included modified Tsvetkova (MT), Park and Chapman (PC), and undiluted. Analyses of four response variables—percent viable sperm (viability), percent motile sperm (motility), curvilinear velocity (VCL), and ATP content—were determined on the day of arrival in the laboratory and then every other day for 7 d in 2008 and 21 d in 2009. The experiments were conducted in a split-split-plot design to examine dilution treatment, gas atmosphere, and repeated measures across days, and linear analyses of covariance models were fit to the data after appropriate transformation. Storage of sperm in an oxygen atmos...