Fall Bloom Phenology and Magnitude Influence Haddock Recruitment On Georges Bank

The haddock (Melanogrammus aeglefinus) stock on Georges Bank in the northwest Atlantic is characterized by extremely large recruitment events relative to spawning stock biomass. Recent work has indicated that the dynamics of the preceding fall bloom may have explanatory power to describe these events. In this paper, we re-examine the hypothesis that fall phytoplankton dynamics affect the recruitment of haddock, examine the temporal and spatial characteristics of the fall phytoplankton bloom on Georges Bank, and examine how the incorporation of these fall bloom dynamics increase the precision of the stock-recruit relationship. Fall bloom characteristics vary considerably across Georges Bank with earlier occurring and larger magnitude blooms occurring on the northern flank. On average, fall blooms start on day 273 (September 29) and last approximately 50 days. There was a strong correlation detected between bloom start date and bloom magnitude with recruitment. The inclusion of bloom dynamics, most notably bloom magnitude, into the stock-recruit relationship resulted in increased model precision. The analysis of the fall bloom on Georges Bank provides a valuable predictive index for recruitment strength of haddock and potentially added utility for the assessment of this stock.