Recruitment Variability and Its Implication for Managing and Rebuilding the Georges Bank Haddock (Melanogrammus aeglefinus) Stock

Abstract

The Georges Bank haddock (Melanogrammus aeglefinus) fishery has fluctuated dramatically since the early 1960's. Abundance declined from the mid-1960's to the mid-1970's, partially recovered, and has declined again since 1980. In general, poor year-classes have been associated with a low spawning biomass although the relationship is variable. The fishery was simulated by using the Baranov catch equation, constant growth and natural mortality, and stochastic levels of recruitment whose probabilities correspond to historic patterns in the stock and recruitment data. Simulations suggest a low probability for stock recovery and improved yield under current conditions (F ≈ 0.5). Recovery time increased with increases in fishing mortality (F), and beyond F = 0.40 recovery is unlikely within 25 yr. With recruitment of a very large year-class (100 million fish) an initial strategy providing for a relatively low level of F(= 0.10) for 3−5 yr, followed by exploitation at historically sustainable levels (F = 0.35), would result in stock recovery. With recruitment of a smaller year-class (50 million fish) low initial levels (F = 0.10) and subsequent management at or near F0.1 (F = 0.26) would be required to initiate stock recovery and reasonable harvest levels in future years.