MEPS 164:229-235 (1998)  -  doi:10.3354/meps164229

As in most populations of bivalves, year-to-year variation in recruitment is large in the tellinacean Macoma balthica (L.). During the period of observation (1973 to 1996), high densities of recruits (numbers of spat, 0-year-class, per m² in late summer) were observed after 3 severe winters (1979, 1985, and 1987) and also in 1991, which was a normal winter, whereas recruitment failed after all of the 5 mildest winters of the period of observation (1974, 1988, 1989, 1990, and 1995). As fecundity (the number of spawned eggs per female) also varies strongly in response to winter temperature in M. balthica, we studied to what extent the large year-to-year variation in recruitment can be explained in terms of temperature-influenced variation in fecundity. To this end, we related both mean annual egg numbers per female (fecundity) and per m² (egg density) to subsequent recruitment data during the 1973 to 1996 period in a population at Balgzand, a 50 km² tidal flat area in the southwestern part of the Dutch Wadden Sea. Water temperatures in winter influenced individual egg production (winter temperature was negatively correlated with fecundity) and, consequently, total egg production of the population (stock size was not related to winter temperature). Although a substantial part (37%) of the year-to-year variation in recruit densities could be explained by interannual variation in winter temperatures, only a minor part of recruitment variation (7%) was explained by variation in egg density. Thus, the numbers of adults and the total number of eggs spawned in a certain year are poor predictors of subsequent recruit abundance. The significant effect of winter temperature on recruitment cannot be explained by the winter-temperature-governed fecundity and total egg production.

Macoma balthica · Fecundity · Stock-recruitment relationship · Winter temperature · Stock size