Date of Degree
Flatfishes; Otolith; Pleuronectidae; Predation; Winter Flounder
In this dissertation, sagittal otoliths were used as a lens to examine latent life history patterns in winter flounder (Pseudopleuronectes americanus) and also as a means of interpreting the species' relationship to their abiotic and biotic environment. Otoliths provide a unique and powerful perspective into the lives of the telost fishes, because they permanently record the spatial and temporal histories through sequential growth patterns from conception to capture. The patterns of growth and dormancy in the otolith are regulated by endogenous and exogenous rhythms, and as the otolith grows, trace elements are absorbed from the ambient environment and incorporated into the calcium carbonate (CaCO3) matrix. Hence, concentric bands in the otolith reliably indicate age and growth conditions similar to the annuli in trees, whereas the chemical chronology contained within the CaCO3 crystal can function as a geochemical tag, to permit retrospective tracking of a fish's movements and reconstruction of its environmental history.
The first chapter in this study demonstrates that winter flounder sagittae are not morphologically, nor are they chemically identical, which is an essential distinction that sets them apart from those found in bilaterally symmetrical fishes. This finding has important implications when using otolith chemistry to investigate population structure of winter flounder and other flatfishes, because indiscriminate use of either otolith can bias statistical results. Consequently, method standardization is recommended when performing otolith chemistry in flatfishes. Furthermore, the results of this investigation provides evidence that the blind-side otolith in flatfishes may be absorbing chemicals differently from their eyed-side counterparts, though these results warrant further testing.
In the second chapter, otolith microchemistry is utilized to examine the fine-scale stock structure of winter flounder that were sampled from the coastal margins of Long Island and surrounding areas. Using otolith microchemistry in this manner, group membership was recognizable an on a scale of tens of kilometers with a statistical accuracy that ranged from 83-87% depending upon spatial dimensions when re-classifying the specimens back to their location of capture. The second part of this chapter examines the feasibility of using otolith microchemistry with specific elemental markers to make qualitative assessments of inshore habitat of winter flounder. Through this investigation, it was revealed that some of the most chemically contaminated bodies of water still make important contributions to winter flounder recruitment, and juvenile growth in these systems can potentially exceed growth patterns in more pristine locations.
The last chapter of this dissertation looks at the age and growth structure of winter flounder in the Hudson River Estuary (HRE) and western Long Island Sound (WLIS) and compares those results to several large-scale surveys that were performed last century and collectively form the historical record of winter flounder in New York waters. The ensuing results of this analysis show that winter flounder in the HRE and WLIS have incurred a faster growth rate, and larger, if not older fish comprise a greater percentage of the population than they did during the early and middle decades of the twentieth century. The increasing size-at-age shown by winter flounder in the HRE and WLIS correlates with a release from intra-specific competition and increasing pressure generated by size-selective mortality imposed by a resurgent and newly emerging suite of predators. Finally, the conclusions of this thesis summarize the results of these investigations and discuss potential directions for future research.
Jackman, George William, "The Ecology Of Winter Flounder From An Otolith Perspective" (2015). CUNY Academic Works.