The interaction between ocean warming and spawning latitude on U.S. Northeast Shelf black sea bass (Centropristis striata) energetics and reproductive potential throughout the spawning season

Ocean warming is driving fish distribution shifts on the U.S. Northeast Shelf (NES) creating adverse consequences for local economies, livelihoods, and ecosystems. Black sea bass (BSB), a prominent NES fish, that range from Cape Hatteras, North Carolina to the Gulf of Maine, are exhibiting a northward range expansion potentially tracking optimal ocean temperatures. BSB undergo seasonal migrations whereby they spawn in inshore from late spring through early fall and reside in southern offshore waters during the winter. Migration distance and temperature differences along their range can drive BSB to experience different energetic pressures throughout their spawning season. BSB were collected throughout the spawning season in Virginia (VA), Delaware (DE), New Jersey (NJ), and Massachusetts (MA). We measured length, weight, sex, gonadosomatic (GSI) and hepatosomatic indices (HSI), percent-dry weight (a proxy for energy content) and total lipid energy for muscle, liver and gonad. BSB collected in VA and DE were found further offshore and in deeper, colder (9-16°C) water, and BSB in NJ and MA were collected in shallow, warm (12-24°C) water. Female BSB were in better condition than males in all locations seen by higher relative condition and liver energy. For pre-spawning BSB, GSI and HSI was highest in DE and VA, but GSI plummeted in VA for the duration of the spawning season. Liver and muscle energy was lowest in MA pre-spawning BSB but increased post-spawning compared to VA, DE, and NJ BSB. These results indicate that MA BSB arrived with the lowest energy likely due to the long migration compared to BSB in NJ, DE, and VA with shorter to minimal migration. The increase in liver and muscle energy in MA BSB post-spawning suggests these fish were preparing for their winter migration. DE BSB were in the best spawning condition seen by highest energy in muscle and liver and highest GSI. Altogether, while migration distance may have a larger negative effect on energetics and reproductive output, ocean warming is shrinking suitable habitat in the south where migration distances are shortest.