Hatch date distributions of young-of-year haddock Melanogrammus aeglefinus in the Gulf of Maine/Georges Bank region: Implications for recruitment

Abstract

We determined the hatch dates of young-of-year (YOY) juveniles from the 1995 to 1999 year-classes of haddock Melanogrammus aeglefinus collected in the Northeast Fisheries Science Center fall groundfish surveys in the Gulf of Maine/Georges Bank region. Hatch dates were based on age estimates made by counting otolith daily rings. The average YOY haddock was >200 d old at the time of capture, with estimated hatch dates ranging from mid November to early June. Haddock collected in the Gulf of Maine had mean hatch dates about 1 mo later than fish collected on Georges Bank. Each year on Georges Bank, hatch date frequencies (HDF) of survivors peaked between February and mid March, considerably earlier than the peak in HDF estimated from late-stage eggs. The ratio of the relative HDF of survivors collected in the fall to the relative HDF estimated from late-stage eggs was used to calculate relative survivorship of different cohorts. These data suggest that haddock hatched early in the season had a survival advantage over those hatched later in the year. The 1998 year-class, the largest produced on Georges Bank in the past 20 yr, had one of the latest peaks in HDF of juveniles among the 5 years examined. More survivors were produced in each month of 1998 compared to the monthly averages of the remaining years. In particular, the 1998 year-class benefited from enhanced survival of individuals hatched in the mid and latter portions of the hatch curve, although survival was still highest for individuals originating from the early portion of the hatching curve. © Inter-Research 2005.