In Rough River Lake, Kentucky, some aspects of the ecology of larval and juvenile fishes were investigated from April – August, 1978. Larval fishes were collected weekly from the upper reaches of the lake from the surface and bottom, during daylight and dark periods. Twenty-three species and three categories of unknown larval and juvenile fishes, represented by 177,119 individuals, were collected. White bass and logperch larvae were the first to appear on April 15 with surface water temperatures of 18.5 C. Gizzard shad larvae dominated net collection while Lepomis spp. were the second most abundant. Larvae were primarily concentrated near the surface and taken mostly at night. Larval concentrations were greatest on May 30. Throughout the study, most specimens were collected along the shorelines. Growth rates of most taxa generally lagged early in life but increased greatly after the first 6-8 weeks. Light traps proved to be an effective method of capture for certain species. Piscivory was observed in white bass 10.5 – 25 mm total length on gizzard shad, and logperch 16.5 – 17 mm total length on unknown larvae and suckers.

The eastern oyster (Crassostrea virginica Gmelin 1791) has great ecological and economic importance but populations have declined, especially in Chesapeake Bay, to historically low numbers. Hatcheries strive to produce oysters with beneficial characteristics for supplementation and commercial purposes, both natural and stimulated mass spawning. Unequal contribution of parents in mass spawnings potentially can lead to high levels of inbreeding and a loss of beneficial characteristics in offspring. In this study, we determined microsatellite genotypes for parents (n^parents =24, 49, and 77 parents) and progeny (n=96 each) of three hatchery-produced families and used the data for parental assignment. We observed the presence of more than two alleles per locus for some offspring, yet because genetic analysis software only allows for a maximum of two alleles per locus, we chose the two alleles with the strongest signals. For the three parent “populations,” 71% of alleles had frequencies of <0.05 and observed heterozygosities were lower than expected by an average factor of 0.27. Inbreeding within the various parent populations was similar across the three families ranging from F^IS 0.26–0.43. In all three families, the offspring exhibited greater levels of genetic diversity and lower inbreeding levels than the parents (F^IS 0.14–0.21), and in some cases offspring exhibited alleles that were not present in the parents. Variance in the number of offspring produced per parent was observed for all families and in general, <10% of potential parents (generally 2-5 females and 1-3 males) produced >10% of the offspring. Reproductive success for spawning parents, N^b, determined by three methods, ranged from 0.07 to 0.27. As the number of parents per family increased, a higher proportion of parents failed to produce offspring. Across all three families, the average effective number of breeders was N^b = 7.1 and the level of reproductive success was inversely proportional to the number of potential parents. This finding implies that to maintain high levels of diversity and beneficial characteristics in the offspring (and to avoid the chance of unintentional inbreeding), hatcheries should perform more spawnings with fewer parents.

No description available.

No description available.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / A combination of overexploitation and destructive fishing practices, such as bottom trawling, have depleted native populations of groundfishes in coastal New England and reduced benthic community diversity. The Stellwagen Bank National Marine Sanctuary (SBNMS) in the southern Gulf of Maine is partially overlapped by the Western Gulf of Maine Closed Area (WGMCA). The WGMCA is closed to commercial fishing for groundfishes managed under the Northeast Multispecies complex and the use of bottom trawling fishing gear is prohibited to protect essential fish habitat. This has reduced fishing pressure and benthic disturbance levels. The area of the SBNMS outside of the WGMCA is still disturbed by intensive commercial fishing for much of the year. Key questions for this area are (1) How does the higher level of disturbance in areas outside of the WGMCA affect SBNMS groundfish communities?, (2) Is the WGMCA effective at increasing the diversity, abundance, and biomass of groundfishes in the SBNMS?, and (3) How does the decrease in disturbance impact groundfish trophic ecology? A comparison of the groundfish communities inside and outside of the WGMCA within the SBNMS was carried out via trawl sampling. Results show that groundfish communities are more diverse inside the WGMCA than outside. Additionally, several commercial groundfish species had higher abundance and/or biomass inside the WGMCA. Stable isotope analyses showed that prey items differed for some species inside and outside of the WGMCA, but trophic levels were unaffected. Finally, stable isotope analyses of five groundfish species provide evidence that groundfishes may display a high level of foraging area fidelity. Primary conclusions include: (1) the protection of groundfish habitats from trawling disturbances paired with reduced fishing pressure will result in increases in community diversity and abundances of groundfishes, (2) groundfish ecology should be considered on a small geographic scale due to apparent site fidelity, and (3) if the entire SBNMS were closed to bottom trawling and commercial fishing, it could help to rebuild overexploited groundfish populations in the southern Gulf of Maine and serve as a source population for the remainder of the Gulf of Maine and adjacent shelf environs. / 2031-01-01

This study doubles the known diversity of nemertean species in one region along the northeast Pacific coast by utilizing the often over-looked larval life-history stage. Prior to this work, the nemertean fauna in this region was believed to be well described; however, previous assessments were based on adult life-history stages only and significantly underestimated the real diversity. With this dissertation, we update what is known about nemertean diversity and expand upon this “life-history” approach to describe new species, identify and describe larval forms, and speculate on the phylogenetic relevance of nemertean larvae. A considerable amount of new diversity takes the form of cryptic species complexes, where existing descriptions include characteristics of several species. Micrura alaskensis, a common intertidal nemertean and an emerging model system for developmental studies, existed as a species complex consisting of five species. In this dissertation we designate a new genus, re-describe M. alaskensis, and describe four new species in this complex. In doing so we make accurate identification possible for future comparative research. The complete development of few nemertean species was known before this project began, thus few species could be identified as larvae. We have identified over 30 nemertean larvae using both embryological and DNA barcoding approaches in this work. Intriguingly, many wild-caught larvae could not be matched to species previously reported from this region and instead contribute to previously unknown diversity. This new diversity includes species previously reported only from distant geographic regions as well as species new to science. The first record of a hubrechtid on the west coast of North America and the identification of two new species in the currently monotypic genus Riserius were revealed in larval assessments. Aside from increasing known species-level diversity, we revealed novel larval types. Barcoding larvae allowed us to place larval morphotypes into a phylogenetic context and identify potentially useful larval synapomorphies for nemertean phylogenies. Our results emphasize the importance of a life-history approach to biodiversity assessments for all species with biphasic life-cycles. This dissertation includes published and unpublished co-authored material.

Cheung, Man Kit. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 81-93). / Abstracts in English and Chinese. / Abstract (English) --- p.I / Abstract (Chinese) --- p.III / Acknowledgements --- p.V / Table of contents --- p.VI / List of figures --- p.IX / List of tables --- p.XI / List of Appendices --- p.XII / Chapter Chapter 1. --- General introduction --- p.1 / Chapter 1.1. --- Picoeukaryotes --- p.1 / Chapter 1.2. --- Conventional characterization techniques --- p.1 / Chapter 1.3. --- Cloning and sequencing approach --- p.3 / Chapter 1.3.1. --- Applications in prokaryotic plankton --- p.3 / Chapter 1.3.2. --- Applications in eukaryotic picoplankton --- p.3 / Chapter 1.4. --- Variations in diversity with environmental factors --- p.5 / Chapter 1.5. --- Study site --- p.6 / Chapter 1.6. --- Objectives --- p.8 / Chapter Chapter 2. --- Materials and methods --- p.9 / Chapter 2.1. --- Study site --- p.9 / Chapter 2.2. --- Sample collection --- p.9 / Chapter 2.3. --- DNA extraction and 18S rRNA gene amplification --- p.11 / Chapter 2.4. --- Clone library construction and screening --- p.12 / Chapter 2.5. --- Sequencing and phylogenetic analysis --- p.13 / Chapter 2.6. --- Statistical analyses --- p.14 / Chapter Chapter 3. --- Results --- p.15 / Chapter 3.1. --- Hydrological parameters of study site --- p.15 / Chapter 3.2. --- Clone libraries --- p.15 / Chapter 3.3. --- Higher-level taxonomic distribution --- p.21 / Chapter 3.4. --- Phylogenetic affiliations of OTUs --- p.22 / Chapter 3.4.1 --- Alveolates --- p.35 / Chapter 3.4.2 --- Stramenopiles --- p.36 / Chapter 3.4.3 --- Rhizaria --- p.36 / Chapter 3.4.4 --- Other lineages --- p.37 / Chapter 3.4.5 --- Novel higher-level groups --- p.38 / Chapter 3.5. --- Diversity estimates of picoeukaryotes --- p.39 / Chapter Chapter 4. --- Discussion --- p.42 / Chapter 4.1. --- Picoeukaryotic diversity --- p.42 / Chapter 4.1.1 --- Overall diversity --- p.42 / Chapter 4.1.2 --- Diversity of individual taxonomic groups --- p.44 / Chapter 4.1.2.1 --- Most represented lineages --- p.44 / Chapter 4.1.2.2 --- Other photosynthetic lineages --- p.52 / Chapter 4.1.2.3 --- Other non-photosynthetic lineages --- p.55 / Chapter 4.1.2.4 --- Novel higher-level lineages --- p.56 / Chapter 4.2. --- Spatial and seasonal variations of picoeukaryotes --- p.58 / Chapter 4.2.1 --- Spatial variations --- p.59 / Chapter 4.2.1.1 --- Compositional variations --- p.60 / Chapter 4.2.1.2 --- Variations in diversity --- p.61 / Chapter 4.2.2 --- Seasonal variations --- p.65 / Chapter 4.2.2.1 --- Compositional variations --- p.65 / Chapter 4.2.2.2 --- Variations in diversity --- p.66 / Chapter 4.3. --- Methodological aspects --- p.67 / Chapter 4.3.1 --- Sample collection --- p.67 / Chapter 4.3.2 --- PCR amplification --- p.68 / Chapter 4.3.3 --- Cloning and RFLP screening --- p.69 / Chapter 4.3.4 --- Statistical estimates --- p.71 / Chapter 4.3.5 --- Future directions --- p.71 / Chapter Chapter 5. --- General conclusion --- p.73 / References --- p.81

No description available.

No description available.

The blue crab Callinectes sapidus supports one of the most important fisheries in the Chesapeake Bay and is the leading contributor to blue crab landings in the United States. Assessment and management of blue crab stocks has been hampered by a lack of estimates of natural mortality rates, a key parameter in assessment models. In Chapter 2, we demonstrate that the approach used for estimating natural mortality that had been used in past assessments was flawed, and provide justification for a superior alternative. In Chapter 3, we synthesize our current understanding of natural mortality rates in adult blue crab and provide a suite of estimates for the Chesapeake Bay stock. Our estimates were used in the 2005 assessment for this stock, and the methods and estimates can provide guidance for assessments of the same or other species. In addition to estimates of natural mortality for adult blue crab, the short turnover time in the stock makes it necessary to consider changes in natural mortality rates with size or age. Current assessment models use an annual time step, which smooths over the changes in natural mortality that occur during ontogeny. Some crabs reach an exploitable size within the first year of life, and smaller crabs are expected to have higher natural mortality rates. In addition, natural mortality is known to vary seasonally, being highest in Chesapeake Bay during the summer months when predators are most abundant and crabs are molting frequently. to include size-dependent mortality in more realistic population dynamics models, we estimated mortality rates of juvenile crabs through field experiments (Chapter 4). In 2005 and 2006, we estimated mortality rates of seven cohorts of hatchery-reared juveniles in two tidal marsh creeks along the York River, Virginia during the summer and fall. Juvenile mortality rates were orders of magnitude higher than current estimates of adult mortality rates and were highest in the summer. Our results reinforce concerns about the adequacy of current assessment models and provide estimates of mortality that can be used to guide future work.