Population characteristics of unfished waved whelk (buccinum undatum) on the U.S. Mid-Atlantic continental shelf: a case study for comparison to global fished stocks

Marine fishes and invertebrates are an essential human food resource and are becoming more important as the human population continues to grow. As the climate continues to change, the overall impact of these changes on fisheries is unknown. It is necessary to understand the effects of these changes on fisheries productivity to identify the amount of fishing that can be sustainably prosecuted today and into the future. Data documenting pre-exploitation life-history traits are essential to understand how a population operates in the absence of fishing. This information is rarely collected prior to exploitation but is critical for sustainable fisheries management. This dissertation documents a broad range of biology and ecology of the unfished waved whelk (Buccinum undatum) population along the U.S. continental shelf. Some of these findings are directly relevant for future U.S. management of waved whelk. In addition to the importance of this information in future sustainable stock assessments, these data from an unfished population can serve as a model to understand the impacts of fishing and climate on other heavily exploited populations. This dissertation uses waved whelk as a model species to examine the population dynamics of a benthic invertebrate in a rapidly changing climate and the future implications of a warmer ocean. The second chapter of this dissertation describes the population structure of B. undatum in the United States Mid-Atlantic via an examination of the species range, size structure, sex ratio, and size of sexual maturity. Estimates of size of sexual maturity for B. undatum from this study and other regions of the world were compiled and demonstrate that this species' maturity size is highly variable. This chapter uses other managed B. undatum populations as examples to discuss whether a national (broad-based) catch size regulation provides sufficient protection to the spawning stock and decreases the probability of overfishing in whelk fisheries. Reproduction occurred in spring and early summer in this population of B. undatum, representing the southern-most extent in the range of this species in the Northwest Atlantic Ocean. The U.S. reproductive development timing pattern identified in this study was further compared globally to other stocks as a means of understanding the range of reproductive phenotypes in the world. Whelk in the Mid-Atlantic Bight experiences spawning and development at ~7–8°C; temperatures warmer than Canadian populations and cooler than some U.K. conspecifics. In the fourth chapter of this dissertation, the size-at-age and climate-growth relationships were modeled for waved whelk (Buccinum undatum) populations within the Mid-Atlantic Bight using annual growth rings observed in statoliths. Growth data of this unfished population provides an opportunity to explore gradients of global fishing intensity and how different amounts of exploitation have affected targeted populations. The growth curves fit to Mid- Atlantic Bight population appear to differ from other assessed populations, possibly due to a timing difference in hatching. Use of age-length information in future Mid-Atlantic Bight stock assessments will allow for better management and sustainability of the whelk fishery. A statolith chronology, which spanned ten years, was developed using mixed-effects modeling to explore the influence of temperature variation on growth during ecologically relevant periods. Growth increased with higher annual temperatures; however, specific seasonal bottom temperatures had varying effects on growth. It appears that whelk in this region possess sufficient growth plasticity to adapt to warmer conditions throughout the year. Still, increased warming during specific seasons may depress older individuals' growth, potentially affecting fitness and population persistence. This dissertation fills important data gaps by collecting information on baseline life history, reproductive timing, and whelk growth in the Mid-Atlantic region of the United States. The population examined herein represents the southern-most extent of waved whelk range in the northern Atlantic. Waved whelk are a cold-water species, and the warming bottom waters of the Mid-Atlantic could cause mortality and shifts in its range if temperatures warm sufficiently. Studying this population on the edge of the animals’ range could be an important key to understanding the species’ persistence amid anthropogenic disturbance. These findings are directly relevant for future management of waved whelk along the U.S. Mid-Atlantic continental shelf. Some provide comparison data to other global whelk populations, which span a range of exploitation ask broad ecological questions about fisheries' interactions.Ph.D.Includes bibliographical reference