Master of Science / Department of Biology / Martha E. Mather / Determining patterns and drivers of organismal distribution and abundance are fundamental and enduring challenges in ecology, especially for mobile organisms at a ‘scape scale. To address the problem presented by individuals whose distributions are dynamic across large geographic areas, here I tracked 59 acoustically-tagged migratory striped bass (Morone saxatilis) with an array of 26 stationary receivers in Plum Island Estuary (PIE), MA. Specifically, I asked (1) how these predators were distributed across the estuarine seascape, (2) if these fish used three types of geomorphic sites (exits, confluences, and non-confluences) differently, (3) if distinct types of individual distributional “types” existed, and (4) if fish within distinct distributional groups used geomorphic site types and regions differently. Based on three components of predator trajectories (site specific numbers of individuals, residence time, and number of movements), striped bass were not distributed evenly throughout PIE. Confluences attracted tagged striped bass although not all confluences or all parts of confluences were used equally. Use of non-confluences sites was more variable than exits or confluences. Thus, geomorphic drivers and regions link mobile organisms to physical conditions across the seascape. Based on spatial and spatial-temporal cluster analyses, these striped bass predators clustered into four seasonally-resident distributional types. These included the (1) Rowley River group (fish that primarily resided in the Rowley River), (2) Plum Island Sound group (fish that primarily resided in the Middle Sound region), (3) Extreme Fidelity group (fish that spent most of their time in PIE at a single receiver location), and (4) the Exploratory group (fish that showed no affiliation with any particular location). These distributional groups used geomorphic site types and regions differently. Thus, my data show a rare link between behavioral (i.e., individual animal personalities) and field ecology (seascape geomorphology) that can advance the understanding of field-based patterns and drivers of organismal distribution.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 134-143). Also available via the Internet.

Comparative ecology and interspecific competition were examined between two sympatric congeners, Sebastes caurinus Richardson 1845 (copper rockfish) and S. maliger (Jordan and Gilbert 1880) (quillback rockfish) in Saanich Inlet, British Columbia, Canada, from 1986-1990. Ecological profiles were constructed through analyses of depth distribution, habitat and species associations, activities, feeding habits, gut allometry, growth, and reproduction. Interspecific competition between copper and quillback rockfish was examined by experimentally manipulating the densities of one or the other species on rocky reefs in Saanich Inlet where they were sympatric. The Pisces IV submersible was used to survey the distribution of rockfish in relatively deep-water (21-140 m) in Saanich Inlet. Copper and quillback rockfish were sympatric in water depths of 21-65 m. They occurred in association with one another the majority of the time (>90%) and their densities were greatest over areas of complex substrate. Size of copper and quillback rockfish was positively correlated with increased depth, primarily due to the absence of small fish in deeper waters. Both species were observed most frequently perched on open substrate or hovering in the water column. Copper rockfish were observed swimming more frequently than quillback rockfish. Copper and quillback rockfish primarily consumed demersal crustaceans throughout the year. Copper rockfish consumed a greater proportion of pelagic fishes than quillback rockfish, whereas quillback rockfish had a greater proportion of pelagic crustaceans in their diet. Levins' (1968) measure of niche breadth of the diet (by mass), as standardized by Hurlbert (1978), was narrow (0.19-0.20) to moderate (0.32-0.51) for quillback and copper rockfish respectively, during spring, summer, and fall. In the winter it was extremely narrow (0.02) for both species due to their feeding predominantly on one prey type, juvenile herring (Clupea harengus) . The Simplified Morisita Index of niche overlap (Horn 1966) in feeding habits (by mass) was relatively high (>0.55) throughout the year, and particularly during the winter (0.99). This high niche overlap in the winter occurred when large schools of juvenile herring were available in the environment and were probably not a limited resource. Extensive niche overlap between copper and quillback rockfish may therefore indicate an abundance of a shared resource rather than competition for the resource. Copper and quillback rockfish consumed the greatest quantity of food during the winter when feeding on juvenile herring, although quillback rockfish consumed significantly less food mass than copper rockfish in the winter. A greater proportion of quillback rockfish were collected with food in their stomachs during the spring and summer, when the numerically dominant food items were pelagic crustaceans. The importance of fish prey in the diets of both copper and quillback rockfish increased with size. Copper rockfish had a shorter intestine and larger stomach relative to similar-sized quillback rockfish. This suggested that the gastrointestinal tract of copper rockfish was better suited to holding and digesting fish and larger crustaceans than quillback rockfish, an observation consistent with differences in their feeding habits. Copper and quillback rockfish had similar growth patterns with no readily identifiable species-specific and sex-specific differences. Both sexes of both species attained asymptotic lengths of 30-31 cm total length and had similar growth coefficients (0.141-0.187). Within each sex, copper rockfish had a smaller increase in mass per unit of body length than quillback rockfish, indicative of a more pelagic lifestyle for copper rockfish. Estimated lengths at first and 100% sexual maturity for female and male copper and quillback rockfish were similar. Male copper rockfish were ripe, and potentially inseminated females, in January and February. Female copper rockfish were found to be carrying fertilized eggs in April and May, and gave birth to their young primarily in June. The reproductive cycle of quillback rockfish preceded that of copper rockfish by approximately one month, with parturition for quillback rockfish occurring mainly in May. The fecundity of copper and quillback rockfish was similar, with a 30-cm fish giving birth to approximately 90,000 young. Visceral fat cycles of mature female copper and quillback rockfish were complementary to their cycles of gonad maturation and increases in gonad size, indicating that they use visceral fat stores as a source of energy for maturation of their eggs and nourishment of their developing young. Visceral fat cycles of mature males were mainly coincident with the maturation and size increase of their gonads, indicating that they did not use visceral fat reserves in the maturation of their gonads. Male rockfish secondarily may have used their fat reserves as an energy source during the period when they were ripe, perhaps for mating activities. Visceral fat accumulation and dissipation in immature males and females appeared to be primarily related to periods of feeding. Interspecific competition between copper and quillback rockfish was asymmetrical, seasonal, and transitory, based on experimental manipulations of the densities of the congeners in natural populations. Copper rockfish did not have a competitive effect on quillback rockfish, but quillback rockfish had a weak competitive effect on copper rockfish. This effect was apparent only during the fall, was strongest in the fall immediately following the density manipulations, and appeared to weaken in the subsequent fall season. The seasonal competitive effect may have been caused by copper rockfish moving onto the study reefs (18-31 m depth) from shallower waters (<20 m) during the fall and winter, creating a short-term 'ecological crunch' in which food or space resources were limited. Overall, comparative ecological profiles of copper and quillback rockfish exhibited a large degree of overlap. Differences observed between them were small but consistently indicated that copper rockfish had a more pelagic lifestyle than quillback rockfish. The otherwise high degree of similarity between the two congeners, however, did not translate into sustained interspecific competition. Ecological theory purporting a major role for interspecific competition in structuring fish communities was therefore not supported by experimental manipulations of population densities of deep-subtidal, temperate zone rockfishes. The asymmetrical, seasonal, and transitory occurrence of weak interspecific competition demonstrated that competition between these rockfish species is dynamic, and cannot account for the pattern of species association. Alternative hypotheses based on the importance of intraspecific competition, predation, or environmental variability must therefore be considered. / Graduate

The method for the determination of total mercury in biological material described in this paper comprises a destruction of organic matter by wet digestion, a reduction of the mercury by stannous sulfate, and circulation of the displaced mercury vapor in a closed system directly connected with an atomic absorption spectrophotometer Seven tissues from ten samples of locally obtained Roccus saxatilis (striped bass) were analyzed, and a three-fold elevation of mercury levels in the liver over the levels in the filet noted. See Table XIX for a comparison of the high, low, and average values for each tissue.

This is the first study to assess how the coastal migratory stock of striped bass (Morone saxatilis) uses non-natal New England estuaries during their foraging migration. Using hydroacoustic telemetry from June through October in Plum Island Estuary, Massachusetts, I examined how long coastal migratory striped bass stayed throughout the seasons, if they were equally distributed, if individual striped bass were distributed differently, and if distribution changed with season, tide, or light. Striped bass, ages 2-5 (300-480 mm), were tagged with VEMCO transmitters in the spring and summer of 2005 (N=14) and 2006 (N=46). They stayed for an average of 66 days in 2005 (SE=7.6) and 72 days in 2006 (SE=6.2). Of the fish tagged in 2005 and 2006, 60% remained for longer than 30 days. This might reflect two striped bass migration strategies: 1) transient migration, in which striped bass visit many estuaries, and 2) estuary-specific, in which they reside in a single location for the summer. The amount of time the striped bass spent in six reaches delineated within the estuary was quantified. Striped bass were not evenly distributed across these reaches. Instead, they spent the most time in the mid Plum Island Sound and lower Rowley River reaches in both years. Three different uses of PIE were observed. Some striped bass stayed briefly (5-20 d; N=24), some stayed primarily in the Rowley River (N=14), and others stayed primarily in Plum Island Sound (N=22). Striped bass use of the mid Plum Island Sound and lower Rowley River reaches remained consistently high in spring and summer, but decreased in fall, while use of the lower Plum Island Sound did not vary much. Use of other reaches varied seasonally. Tide and light were less associated with distribution, but in the summer the Rowley River use-group increased utilization of tidal creeks during the day, though not at high tide. These three use-groups identified in Plum Island Estuary may be foraging contingents that may learn how to forage in specific parts of the estuary demonstrated by over half the striped bass remaining for much of the summer and congregating in distinct areas.

No description available.

This investigation examined the adequacy of the forage base to meet current demand of piscivores in Smith Mountain Lake, Virginia. Surplus production, or the maximum sustainable supply, of alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) were determined using data on the biomass, growth, and mortality of each species. Mean hydroacoustic alewife biomass from 1993-1998 was 37 kg/ha and mean gizzard shad cove rotenone biomass from 1990-1997 was 112 kg/ha. Mean annual alewife surplus production was determined to be 73 kg/ha and mean annual gizzard shad surplus production totaled 146 kg/ha. Bioenergetics modeling and population density estimates were utilized to derive the annual food consumption (realized demand) of the two most popular sport fish in the system, striped bass (Morone saxatilis) and largemouth bass (Micropterus salmoides). The striped bass population consumed 46 kg/ha of alewife and 27 kg/ha of gizzard shad annually. Largemouth bass ate 9 kg/ha of alewife and 15 kg/ha of gizzard shad annually. Annual consumption by ancillary predators was estimated to be 13 kg/ha of alewife and 35 kg/ha of gizzard shad. Prey supply to predators is limited by morphology, behavior, and distribution. The cumulative effect on prey availability of these three factors, in addition to consumption by other predators, was quantified. For largemouth bass, available supply of alewife and gizzard shad exceeded demand by 20% and 53% respectively. For striped bass, available supply of gizzard shad surpassed demand by 30% but available alewife supply was only 4% greater than demand. Annual demand of all predators was 94% of total available clupeid supply. Striped bass stockings were increased by 50% in 1998 and will remain at this level in the near future. A predator-prey simulation model of alewife and striped bass populations was developed to explore the consequences of increased predator demand. This model incorporated dependencies between alewife abundance and mortality and the mortality, abundance, and growth of striped bass. Model output showed that a 50% stocking increase has a near-zero probability of increasing the mean annual number of legal and citation striped bass in Smith Mountain Lake. / Ph. D.

Sunshine and palmetto bass (different crosses of hybrid striped bass) were used to determine immunologic, hematologic and serum chemistry changes under different culture conditions. The kinetics of the humoral immune response was determined for sunshine bass acclimated to 10, 18, 24, 29°C, and to elevated ammonia (0.15 mg/L NH3) and elevated nitrate (200 mg/L). These conditions are frequently encountered in aquaculture situations. Cooler temperatures decreased both the magnitude and onset of the humoral response, being lowest at 10°C, intermediate at 18°C, the highest at 24 and 29°C. Elevated ammonia did not affect the immune response, while elevated nitrate decreased antibody production to the level of the 18°C response. Hematologic reference intervals were determined for sunshine bass in tanks and recirculating systems, and palmetto bass in tanks. Serum chemistry reference intervals were determined for sunshine bass in tanks, recirculating systems and cage systems. Greater differences were observed in reference intervals between the culture systems, than between the two types of hybrid. To determine if environmental factors influenced the differences seen in the reference, sunshine bass were acclimated to 10, 18, 24, 29°C, elevated ammonia (0.15 mg/L NH3) and elevated nitrate (200 mg/L). The hematology and serum chemistry profiles of these fish were compared with the reference intervals for sunshine bass in tanks. Leukocyte, lymphocyte and monocyte counts at 10°C, and glucose and calcium at 10 and 18°C deviated sufficiently to suggest generating separate reference intervals at these temperatures. In the nitrate treated fish, creatinine levels were elevated and chloride levels were lower than controls and outside the reference interval. These two responses were presumed to be pathologic changes associated with elevated nitrate levels due to the large deviation in the analytes and the mortalities seen in the nitrate treated fish. The remaining analytes for fish in the different environments were within or slightly outside the reference intervals. These slight changes were presumed to be due to individual variation as the reference intervals were determined for fish under relatively uniform conditions and may not be sufficiently broad to cover fish from more varied environments. With minor modification, the reference intervals should apply to sunshine bass in most situations. / Ph. D.

TRIAL 1 A preliminary study was conducted to evaluate growth, survival and feed conversion of reciprocal cross hybrid striped bass (<i>Morone chrysops</i> female x <i>Morone saxatilis</i> male) cultured in pilot-scale recirculating aquaculture systems. Hybrid striped bass were stocked in nine 12,500 liter recirculating systems at a mean density of 149 fish/m³. Mean weight at stocking was 40.6 g. Overall survival averaged 72.5%. One system experienced 100% mortality due to the loss of the recirculating pump. Three systems experienced significant mortalities in the middle of the study due to unknown causes. Survival was high, averaging 93.5%, in the remaining systems. Mean daily growth rate of 1 g per day and mean feed conversion of 1.67 compared favorably with that reported in the literature for hybrid striped bass. Slow start-up of new biofilters led to a restricted feeding regime and limited growth. Mean fish weight at harvest averaged 262.1 g with total biomass in the tank averaging 452.57 kg. The recirculating system maintained water quality within ranges adequate for good growth, but the stocking density may have surpassed the systems maximum capacity. TRIAL 2 Results from Trial 1 indicated a need to reduce stocking densities. In Trial 2, three densities of reciprocal cross hybrid striped bass, high (144 fish/m³), medium (72 fish /m³) and low (36 fish/m³) were stocked in eight pilot-scale recirculating systems (12,500 L) and evaluated over 224 days. At stocking, mean weights averaged 34.9, 50.8, and 43.4 g for the high, medium and low treatments, respectively. Fish were hand fed a high protein (44%) floating pellet twice daily. Final weights averaged 412.2 g, 541.1 g, and 676.1 g in the high, medium and low density treatments, respectively. No difference in mean weights were detected between the high and medium densities, but those in the low density were significantly greater (p < 0.05) than the medium and high densities. Total biomass was significantly different (p < 0.05) between treatments at the end of the study and inversely related to mean weight gain, averaging 733.8 kg in the high, 483.3 kg in the medium, and 297.9 kg in the low density treatments. The water quality parameters measured were similar among treatments and adequate for good growth. Feed conversions averaged 1.43 and were not significantly different between treatments. Survival averaged greater than 95% in all treatments. The results of this study demonstrated that hybrid striped bass can grow from fingerling to market size in 224 days in recirculating systems at densities of 36 and 72 fish/m³. If environmental conditions are adequately maintained, it is anticipated that higher densities could reach market size in the same time period. Overall results indicate that hybrid striped bass have good potential for culture in recirculating aquaculture systems. / Master of Science

In this report an investigation on the ovaries of three(3) rock fish was discussed; the sampling of eggs within these ovaries was employed to determine the distribution of large and small eggs in each. From Merriman’s report, a general description of the fish, its habits, etc., was presented, showing significant facts that make the striped bass fisheries one of the great industries of the Atlantic Coast. The rock ovaries inspected came from fish taken in May, November and March. Sampling the ovaries was accomplished in the following manner; the ovary was sliced in six (6) cross-sections, and eight (8) samples were taken from each cross-section in order that a thorough study might be made of the egg distribution from place to place within the ovary. The randomized blocks design was used for the analysis. The large, or mature eggs were separated from the small, or immature eggs in each sample and all were counted under an ocular micrometer. From the egg counts the percent of large eggs present was computed for each sample. An Analysis of Variance was run on the data obtained from the samples of these three ovaries. The Analysis of Variance showed that there was no significant difference in the percent of large eggs present between any section or any position in the ovary. Thus, the large and small eggs together form a homogeneous matrix. The most efficient method of sampling from the ovary of the rock fish, as concluded from the findings in this experiment, is to be obtain samples of eggs at random from the ovary. Each sample should contain more than one hundred fifty (150) ova; the number of samples being determined by precision desired. The number of samples are given in Tables 5a, 5b, and 5c depending upon precision . / M.S.