Date of Award

12-2020

Document Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Sciences and Technology

First Advisor

John Mandelman

Second Advisor

Michael Armstrong

Third Advisor

Robyn Hannigan

Abstract

Black sea bass (Centropristis striata) is a demersal marine species that supports extensive commercial and recreational fisheries along the Atlantic coast. A recent expansion into the Gulf of Maine raises questions about this species’ movement and population dynamics in the region. Additionally, the 2016 catch-at-age stock assessment model for the northern stock incorporated a population split at the Hudson Canyon. Though this model better accounts for differences in populations, several issues remain. First, validation of the otolith ageing technique for this stock is incomplete; and, second, the origin of fish that moved into the northern ranges of the Gulf of Maine (GOM) remains unclear.

Error stemming from inaccurate age determinations can have serious effects on age-structured calculations (e.g. growth rate) leading to stock assessments that do not correctly reflect the population. In this study, I validated the black sea bass otolith ageing method using marginal increment analysis and young-of-year annulus measurements. Samples spanned the spatial distribution and age range of the northern stock. Results indicated black sea bass otoliths complete an annual increment, one translucent and one opaque band, in the late spring or early summer. Additionally, the first annulus was validated, an important step in verifying total age that is not present in the current literature for this species.

The natal origin of black sea bass caught in the northern ranges of the GOM was assessed by otolith core trace element and stable isotope microchemistry. Analysis of spawning adult otoliths identified unique chemical fingerprints for the regions north and south of the Hudson Canyon: Southern New England (SNE) and the Mid-Atlantic Bight (MAB), respectively. Black sea bass caught in Maine waters were assigned to a spawning region by matching chemical fingerprints. Overall, 87% were assigned to SNE and 13% to MAB.

This project helps to improve the accuracy and precision of black sea bass otolith ageing practices by validating the method used by agencies and organizations across its distribution. Additionally, this project confirms hypotheses that SNE spawned fish moved north, and further elucidates population composition of the GOM, an area where little is known about this species.

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