Growth and reproduction of the common whelkBuccinum undatumin west Cotentin (Channel), France

Abstract

-The common whelk Buccinum undatum (Neogastropoda, Buccinidae) is widespread along the north Atlantic coasts of France. In west Cotentin (Normandy), an important local fishery exists that depends exclusively on this marine resource and represents about 90% of French whelk production. Despite successive restrictive measures, fishing yields have decreased since 2000. Shell length frequency distributions of Buccinum undatum caught in west Cotentin were studied in 2005 (N = 2910), in 2007 (N = 2032) and in 2009 (N = 4145) ranging from 7 to 85 mm. In order to preserve this fishery and to characterise the whelk stock at this site, the reproductive biology of this species was studied in relation to age, sex and size, for whelks of commercial size (45 to 61 mm) over the complete annual cycle in 2008. Age was determined by reading the number of operculum striae: animals between 45 and 59 mm had 2 to 4 striae. Four reproductive stages were defined for males and females on the basis of histological analysis. The time course of reproductive events was described according to size and sex: the highest percentages of ripe stages were found in October for both sexes. Spawning events occurred between October and December. The shell length that corresponded to 50% of animals having mature gonads (49 mm and 52 mm for males and females, respectively, corresponding to 3 and 4 years old animals) exceeded the minimal landing size (45 mm). Fifty percent maturity was reached for males in their third year and for females in their fourth year. Reproductive investment was evaluated by quantitative analysis of the gonadal thickness or surface and was found to be proportional to shell size. We found that less than 20% of females under 49 mm in length were sexually mature and that these produced only a few eggs. This information, collected in a major fishing area, should assist fishery management decisions.

Whelk (Buccinum undatum L.) stocks around the Island of Jersey, Channel Islands: Reassessment and implications for sustainable management

“…Similarly, Shelmerdine et al's (2007) work in the Shetland Islands and southern England has shown that a large scale EU MLS is not suitable for regional scale management with differing sizes of maturity. Heude-Berthelin et al (2011) also observed spawning to occur mainly between October and December in the Bay of Granville region. Whilst Jersey currently has no closed season, France's closed season occurs in January, and applies to French-registered vessels, wherever they fish.…”

“…We would thus suggest a joint closed season in both Jersey and France, at the same time of year. However we would also suggest this closed season be moved to the spawning period identified by Heude-Berthelin et al (2011).…”

“…1). Heude-Berthelin et al (2011), studying common whelks in the Bay of Granville area, calculated the shell length to 50% maturity as 49 mm for males, at approximately 3 years old and 52 mm for females, at approximately 4 years old. To date there has been no studies around Jersey or the Bay of Granville to study ontogenetic segregation in the area.…”

“…The only significant study on whelk maturity in the region around Jersey was conducted by Heude-Berthelin et al (2011), who also raised some concerns over current management measures for the whelk commercial fishery in the region. One of the principal measures for controlling over-exploitation is the European Union (EU) legal minimum landing size (MLS) of 45 mm shell length.…”

Timing of the reproductive cycle of waved whelk, Buccinum undatum, on the U.S. Mid-Atlantic Bight

“…Some studies examining reproductive cycles of this species have used baited pots for sample collection (i.e. [9,18,64]). Santarelli and Gros [4] indirectly indicate a link between the reduced feeding and onset of reproduction in the French fishery based on catch per unit effort, which severely decreased from August through October.…”