Distribution, abundance and some population characteristics of the ocean quahog, Arctica islandica (Linnaeus, 1767), in the Mecklenburg Bight (Baltic Sea)

摘要

In the Mecklenburg Bight (western Baltic Sea), the ocean quahog, Arctica islandica, constitutes the most important species below the halocline. In 1999 a benthos survey at 95 stations in the Mecklenburg Bight showed a wide distribution of A. islandica at depths between 15.6 and 29.6 m. Mean abundance at these depths was 91 ind./m~2 with a biomass (AFDW) of 15 g/m~2. Maximum densities observed at these depths were 571 ind./m~2 and 120 g/m~2, respectively. The Mecklenburg Bight had an estimated colonized area of 5200 km~2 and a total annual production of 26500 t AFDW. In comparison to a data set of the 1960's, we found an increased quahog population. Ocean quahogs ranged from 1.5 to 64 mm in shell length and from 1 to 70 years of age. Growth was relatively slow for the first 40 years. Most (90 percent) individuals in the population measured <30 mm shell length, indicating strong recruitment in the Bight during the past decades. While the highest abundance (most juveniles) was observed in depths between 15 and 20 m, maximum biomass (due to adults) lay between 20 and 25 m. Probably the recruitment zone was displaced from below 20 m to 15-20 m depth in the last decades. Mean quahog wet meat yields was 18.3 percent. The individual ash free dry weightdecreased significantly with increasing shell length from 14.3 percent (<10 mm) to 9.4 percent (>40 mm). All results were compared with data from populations in North Atlantic and adjacent waters.