Overwintering ecology of young-of-the-year winter flounder in Narragansett Bay, Rhode Island

Richard James Bell, University of Rhode Island

Abstract

Winter flounder is an important commercial and recreational species and was once one of the most abundant fish in Narragansett Bay. The stock declined in the mid-1980s paralleling a similar trend throughout southern New England and has shown very little, if any, recovery. Many strong age-0 year-classes failed to survive to age-1 or older and work has indicated that a mortality bottleneck occurs sometime after the summer of the first year of life. This study investigated the diet, lipid content, growth, mortality and distribution of YOY winter flounder during the winter. YOY winter flounder were found to eat throughout the winter and were found with food in their stomachs down to <3°C. Larger individuals did not have a higher proportion of lipids, suggesting that size-based mortality due to starvation did not occur. Lipid content varied seasonally and was potentially related to the available benthic biomass. Individually marked YOY fish in an overwintering growth study suffered very low mortality and grew throughout the winter. Larger individuals at the start of the experiment maintained their size advantage through the study and into the spring. Seasonally varying growth curves based on the von Bertalanffy model provided significantly better fits to the data indicating that YOY winter flounder exhibit temperature-dependant growth. Annual growth and mortality estimates of YOY winter flounder from settlement in June to age-1 the following spring with a length-based model did not exhibit a simple linear relationship with temperature or YOY abundance. Mortality was negatively correlated with growth suggesting that mortality was weakly size-dependent. Mortality was variable between years, however there was no trend with time suggesting that mortality from post-settlement to age-1 is not driving or compounding the decline in Narragansett Bay winter flounder. A generalized additive model found the majority of fish were found in the northern part of the Bay in the fall and moved into the mid and lower parts of the Bay as the temperature declined. During the the coldest months of the year, YOY winter flounder could be found at any depth throughout the Bay, but on average the majority of flounder were found in the deepest areas at the mouth of the Bay. The decline in catch within the Bay and abundance in deep water suggest that YOY fish move into Rhode Island Sound during the winter.

Subject Area

Biological oceanography|Aquatic sciences

Recommended Citation

Richard James Bell, "Overwintering ecology of young-of-the-year winter flounder in Narragansett Bay, Rhode Island" (2009). Dissertations and Master's Theses (Campus Access). Paper AAI3401130.
https://digitalcommons.uri.edu/dissertations/AAI3401130

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