Recent declines in American lobster fecundity in southern New England: drivers and implications

Abstract

Abstract Lobsters in southern New England (SNE) have experienced decades of environmental stressors along with a suite of emerging diseases. We hypothesized that the sublethal effects of physiological stress resulting from increased temperatures have contributed to a decline in reproductive investment in SNE lobsters. Using the presence of epizootic shell disease (ESD) as a proxy for stress, we examined lobster potential fecundity through the number of recently extruded, early-stage eggs and their nutritional quality; realized fecundity based on counts of late-stage eggs nearing hatch; and compared realized fecundity to historical data (1980s) from the region. Generalized linear modeling revealed that female size was a significant predictor of both potential and realized fecundity as expected, but that ESD status did not result in differences in fecundity. Dry weight was the only difference in nutritional content egg–1 between non-diseased and diseased females. There was also no relationship detected between potential fecundity and any nutritional metric from non-diseased females. However, both dry weight and protein were negatively correlated with potential fecundity in diseased females. Most importantly, realized fecundity of recent-day females was significantly reduced compared to the fecundity of historical females, characterized as a 23% decrease predicted by our model. Stressful environmental conditions, particularly temperature, may have contributed to decreased fecundity over a 30-year period in SNE. Our data demonstrate that expectations around the potential for the SNE stock to rebuild need to be adjusted to this new regime of decreased reproductive output and can no longer rely on past estimates of egg production and recruitment.