William A. Lellis

Effect of temperature on survival, growth and feed intake of postlarval spiny lobsters, Panulirus argus

Ten-week growth of postlarval spiny lobsters (initial live weight 0.22 g) was greater (P<0.01) for animals reared at 30°C (final live weight 1.62±0.14 g) than for animals reared at 24, 27 or 33°C (final weights 0.60±0.04, 1.18±0.04 and 0.92±0.16 g, respectively). Suppressed growth among lobsters held at 24°C was due to prolonged intermolt periods and reduced size increments with each molt. Lobsters reared at 33°C had lower survival, smaller molting increments and lower feed conversion than lobsters held at 30°C. Data indicate that optimal growth of postlarval Panulirus argus occurs at water temperatures of 29–30°C, with optimal feed conversion occurring at slightly lower temperatures.

The effects of experimental starter diets with different levels of soybean or menhaden oil on red drum (Sciaenops ocellatus).

Abstract Red drum reared from captive-spawned eggs were used in a 2 × 4 factorial experiment comparing eight diets with soybean oil (SBO) or menhaden oil (MHO) added to a basal diet (about 3.4% lipid from practical ingredients) at 1.5, 5.2, 9.0, or 12.7%. Triplicate groups of 20 early juveniles (mean 0.4 g) were stocked in 1000 litre fiberglass tanks supplied with filtered estuarine water (17–26 °C, mean 22 °C; 15–35‰) and hand fed twice a day to apparent satiation for 56 days. The fish (range 0.3–9.4 g) appeared to utilize up to 1.5–5.2% dietary SBO (in 5.4–8.7% total lipid). With 0.67% EPA + DHA (eicosapentaenoic and docosahexaenoic acids) in the basal diet, no EFA-deficiency signs were observed. Dietary MHO was utilized up to 12.7%, but fish fed diets with more than 1.5% SBO had lower growth rates and increased feed conversion ratios (especially with 9.0 and 12.7% SBO). Diets containing 1.5% SBO or MHO produced the leanest fish (70.5–71.6% protein, 13.0–13.1% lipid, of whole body). Diets containing 9.0 and 12.7% MHO produced the fattest fish (64.5–66.0% protein and 19.1–19.9% lipid). Percent liver lipid (wet) was highest for fish fed diets containing 5.2% SBO (41.4%), 9.0% MHO (36.5%), and 12.7% MHO (35.4%), and lowest with 1.5% MHO (24.0%). Considering the good survival, absence of disease, and excellent general health, this fatty liver condition did not appear to have short-term adverse effects. All fish in the study had fatty livers to some degree, and their liver histological features differed from those of wild fish. Liver lipid reserves might confer some survival advantage to fish released for stock enhancement if the reserves are used during their transition from cultured to wild status. However, if the hepatocyte changes we observed are not reversible, long-term detrimental effects on liver function are possible.

Landscape Determinants of Nonindigenous Fish Invasions

Much has been written about the influence of exotic or nonindigenous species on natural habitats and communities of organisms, but little is known of the physical or biological conditions that lead to successful invasion of native habitats and communities by exotics. We studied invasivity factors in headwater streams of the Susquehanna River West Branch, which drains portions of the northern Appalachian Plateau. A replicated (two major tributaries) 3 × 3 factorial design was used to determine landscape effects of size (stream order) and quality (land use) on abiotic (physical and chemical) and biotic (fish community structure and function) stream attributes. Seven (21%) of thirty-four fish species (brown trout, common carp, mimic shiner, bluegill, smallmouth bass, fantail darter, and banded darter) collected in the eighteen streams sampled were nonindigenous to the basin. Watershed size (stream orders 1, 3, and 5) significantly affected stream geomorphologic and habitat variables (gradient, width, depth, current velocity, diel water temperature, bank overhang, canopy cover, and woody debris density) but not water-quality variables, while land use in watersheds (conservation, mining, and agriculture) significantly affected measured water-quality variables (alkalinity and concentrations of manganese, calcium, chloride, nitrate, and total dissolved solids) but not stream physical or habitat quality. Both watershed size and land use affected fish-community variables such as presence of particular species, species density, species diversity, tolerance diversity, and mean fish size, but in both cases the effect was transparent to native-origin status of fish species. No relationships were found between occurrence of nonindigenous species in watersheds and trophic structure or functional diversity. Therefore, the hypothesis that reduced species diversity increases vulnerability to nonindigenous species was not supported. However, the spatial variation associated with both water-quality and habitat-quality factors was greater in streams with mixed (those with nonindigenous species) than with exclusively native assemblages. These findings suggest that the mechanism for successful invasion by nonindigenous or exotic species is through change in water or habitat quality associated with human or natural disturbances, such as agriculture and mining activities in watersheds. Biotic factors appear to play no or a lesser role in the invasibility of northern Appalachian lotic systems.

The effect of diet on dorsal fin erosion in steelhead trout (Oncorhynchus mykiss)

A 2 × 2 factorial experiment of diet type (krill vs. fish meal) and steroid supplementation (0 vs. 30 μg 17α-methyltestosterone kg−) was conducted to determine the effects on dorsal fin erosion in steelhead trout. Triplicate tanks of 250 fry were fed one of the four diets at a rate calculated to produce 115 g fish in 34 weeks. Fish were transferred to larger tanks when mean density index reached 0.40. Dorsal fin index (DFI, measured as mean dorsal fin height × 100/total fish length) was greater (P < 0.001) among fish fed krill-based diets than for fish fed fish-based diets at weeks 12, 22, and 34 of the trial. Added testosterone decreased (P = 0.04) DPI among fish fed the krill diet at week 12 but otherwise had no effect on fin condition. Addition of testosterone to either diet type decreased (P = 0.02) critical thermal maximum, which is a measure of fish resistance to thermal stress. The results suggest that diet composition can influence the rate of dorsal fin erosion in steelhead trout through a metabolic, behavioral, or combined change.

The effect of dietary protein and lipid source on dorsal fin erosion in rainbow trout, Oncorhynchus mykiss

Abstract A study was conducted to determine the effect of dietary protein and lipid source on dorsal fin erosion in rainbow trout. Seven diets were each fed to four replicate lots of 300 first-feeding fry cultured in 75 l aluminum troughs for 8 weeks. Two basal diets were manufactured with approximately equal nutrient content, one using krill and squid meals and the other anchovy meal as the primary protein-containing ingredients. The meals used to manufacture the diets were separated into two fractions: lipid (ether-extractable); and protein/ash (non-ether-extractable) using a large soxhlet. The fractions were then recombined to create two additional diets; one containing anchovy protein/ash with krill/squid lipid, the other krill/squid protein/ash with fish lipid. A fifth diet recombined krill/squid protein/ash with krill/squid lipid to evaluate effects of the extraction process. Two additional treatments included a diet with a portion of the krill meal replaced by poultry by-product meal, and the basal anchovy meal diet supplemented with sodium, magnesium, and copper. Fish consuming diets containing anchovy meal as the primary protein source gained more weight ( P P P

Newly Documented Host Fishes for the Eastern Elliptio Mussel Elliptio complanata

Abstract The eastern elliptio Elliptio complanata is a common, abundant, and ecologically important freshwater mussel that occurs throughout the Atlantic Slope drainage in the United States and Canada. Previous research has shown E. complanata glochidia to be host fish generalists, parasitizing yellow perch Perca flavescens, banded killifish Fundulus diaphanus, banded sculpin Cottus carolinae, and seven centrarchid species. Past laboratory studies have been conducted in the Midwest; however, glochidia used in these studies were obtained from adult mussels in the Great Lakes or St. Lawrence River basins, or glochidia sources were not reported. The objective of this study was to identify host fishes for E. complanata from streams in the Mid-Atlantic region. We used artificial laboratory infections to test host suitability of 38 fish and 2 amphibian species with E. complanata glochidia from the Chesapeake Bay drainage. Glochidia successfully metamorphosed into juvenile mussels on five fish species: American ...

Host Identification for Strophitus undulatus (Bivalvia: Unionidae), the Creeper, in the Upper Susquehanna River Basin, Pennsylvania

Abstract Hosts for Strophitus undulatus (Bivalvia: Unionidae) were identified through laboratory infestations. Strophitus undulatus had a low degree of host specificity, transforming on 15 of 22 species examined, including three non-native species and one anadromous species. Suitable hosts included five cyprinid species, two salmonids, two centrarchids, two percids and Acipenser oxyrhynchus (Atlantic sturgeon), Ameiurus natalis (yellow bullhead), Cottus cognatus (slimy sculpin) and Notophthalmus viridescens viridescens (red-spotted newt). Ten hosts were previously unknown. No metamorphosis was observed in a control treatment without a potential host. Recovery of juveniles occurred 12–41 d after infestation at 13–18 C. Duration of glocidial attachment to the hosts declined with increasing water temperature.

Effect of dietary ingredient substitution on dorsal fin erosion of steelhead.

Abstract A feeding trial was conducted to determine the effect of supplementing a diet based on hydrolyzed fish meal with either 6% chitin (as ground krill shell), 6% squid meal, or 200 mg carotenoid pigment (canthaxanthin) per kilogram on dorsal fin erosion in juvenile steelhead Oncorhynchus mykiss. Three hundred fry in triplicate tanks were fed one of the four test diets, and 300 fry in a single tank were fed a commercial trout starter diet. The feeding trial was conducted for 15 weeks at a water temperature of 15°C. Growth was significantly higher (P < 0.05) for fish fed the diet containing chitin than for those fed other feeds. Dorsal fin index (100 × mean dorsal fin height/total fish length) was similar among fish consuming the hydrolyzed fish meal diets but lower for fish consuming the commercial formulation. Results suggest that removal of bones from fish meal may influence dorsal fin condition in steelhead, perhaps through altered dietary mineral composition or form.

Behavioral responses of freshwater mussels to experimental dewatering

Understanding the effects of flow alteration on freshwater ecosystems is critical for predicting species responses and restoring appropriate flow regimes. We experimentally evaluated the effects of 3 dewatering rates on behavior of 6 freshwater mussel species in the context of water-removal rates observed in 21 Atlantic Coast rivers. Horizontal movement differed significantly among species and dewatering rates, but a significant species × dewatering interaction suggested that these factors influence movement in complex ways. Species differences in movement were evident only in controls and under slow dewatering rates, but these differences disappeared at moderate and fast dewatering rates. Burrowing behavior did not differ with respect to species identity or dewatering rate. The proportion of individuals that became stranded did not differ among species, but most individuals became stranded under low and moderate dewatering, and all individuals became stranded under fast dewatering. Mortality after stranding differed strongly among species along a gradient from 25% in Pyganodon cataracta to 92% in Alasmidonta marginata. Together, these results suggest that species behavior may differ under gradual dewatering, but all species in our study are poorly adapted for rapid dewatering. Most of the 21 rivers we assessed experienced dewatering events comparable to our moderate rate, and several experienced events comparable to our fast rate. Dewatering events that exceed the movement or survival capability of most mussel species can be expected to result in assemblage-wide impacts. Consequently, the rate of water level change may be important in refining target flow conditions for restoration.

Population Demographics for the Federally Endangered Dwarf Wedgemussel

Abstract The dwarf wedgemussel Alasmidonta heterodon is a federally endangered freshwater mussel species inhabiting several Atlantic Slope rivers. Studies on population demographics of this species are necessary for status assessment and directing recovery efforts. We conducted qualitative and quantitative surveys for dwarf wedgemussel in the mainstem Delaware River and in four of its tributaries (Big Flat Brook, Little Flat Brook, Neversink River, and Paulinskill River). We quantified population range, relative abundance, size, size structure, and sex ratio within each river. We estimated total dwarf wedgemussel population size for the surveyed rivers in the Delaware Basin to be 14,432 individuals (90% confidence limits, 7,961–26,161). Our results suggest that the historically robust Neversink River population has declined, but that this population persists and substantial populations remain in other tributaries. Sex ratios were generally female-biased, and small individuals (<10 mm) found in all rivers ...