Nursery function of Wadden Sea tidal flats for the brown shrimp Crangon crangon

Abstract

The significance of the tidal zone as nursery area for the brown shrimp Crangon crangon became evident during a study on density and size-distribution of predator populations on a 50 km2 tidal flat in the western Wadden Sea (The Netherlands). A clear picture of the nursery system and its function in the annual cycle of brown shrimp is obtained when nursery population-data are combined with experimental growth rates in juvenile C. crangon and their dependence on temperature and body size. Shrimp brood settles in the area during February-August with main arrival during April, May and June; it leaves the tidal zone, at a body length of ca. 30 mm, during July-September. At the end of the year the majority of the new shrimp generation reaches maturity, after which winter spawning leads to settlement of new brood in spring again. The annual cycle thus obtained fits well in the seasonal pattern of commercial shrimp catches in the area. The predominance of winter spawning and the low effect of summer-egg production is explained by the seasonal temperature cycle and its effect on the development of the juveniles at our latitude, as well as by a specific seasonal pattern of predation pressure on shrimp brood in the tidal zone. Spawning cycles in C. crangon along other parts of the European continental coast are discussed

Sex-ratio, seasonality and long-term variation in maturation and spawning of the brown shrimp Crangon crangon (L.) in the German Bight (North Sea)

“…Two reasonably discrete spawning periods within the annual breeding season had been reported to occur in C. crangon (Lloyd andYonge 1947 andHenderson andHolmes 1987 for the Bristol Channel, Meredith 1952 for the Liverpool Bay) with some latitudinal modifications (Kuipers and Dapper 1984). Indications for two broods (winter and summer) were also found by Oh and Hartnoll (2004) in the Irish Sea.…”

Fluctuations of brown shrimp Crangon crangon abundance in the western Dutch Wadden Sea

“…The summer generation might be subject to heavy predation pressure resulting in high mortality and low contribution to the fisheries standing stock (Kuipers & Dapper 1984). In contrast, the larvae originating from winter eggs migrate into shallow nursery grounds where they settle in spring/summer (Boddeke & Becker 1979, Boddeke et al 1976, Feddersen 1993 and grow and increase in mass until autumn (Boddeke 1976, Kuipers & Dapper 1984, Beukema 1992, Cattrijsse et al 1997. Most shrimps reach maturity in the first autumn of life, migrate to overwintering grounds and are recruited into the commercial fishery.…”

“…In the Dutch Wadden Sea, situated at intermediate latitude within the brown shrimp geographic distribution, egg-bearing females can be found all year round, although mainly in summer and winter (Boddeke & Becker 1979, Boddeke 1982, Kuipers & Dapper 1984. The summer generation might be subject to heavy predation pressure resulting in high mortality and low contribution to the fisheries standing stock (Kuipers & Dapper 1984).…”

Changes in distribution and decrease in numbers during migration of the bivalve Macoma balthica

“…A nursery is an area inhabited by many juveniles but few adults of a species. This is typical, for example, for the lugworm Arenicola marina (Farke et al 1979), the shore crab Carcinus maenas (Klein Breteler 1976, Beukema 1991, the shrimp Crangon crangon (Kuipers & Dapper 1984) and the bivalve Macoma balthica (Beukema 1993).…”