Gastropod resource distribution and seasonal variation in trawling grounds off Konkan Malabar region, eastern Arabian sea

Abstract

Gastropod resource distribution and seasonal variation was studied from 2007-2010 based on onboard collection from multiday trawlers operating in Konkan Malabar region along the eastern Arabian sea at various depth (0-50 m, 51-100 m and 101-200 m), for a total of 619 fishing days (32 months). Thirty five species belonging to 18 families and 4 orders were found in different depths. Family Muricidae dominated in all the depth zone. In 0-50 m depth Tibia sp. (45%) dominated, while Turris sps (19.7%) in 51-100 m and Conus sp. in 101-200 m. Highest diversity (Shannon Weiner H (log 2)) was found in 0-50 m depth during post- monsoon season and lowest (1.36) in 101-200 m depth. Gastropod of common occurrence in all the depth zones constituted of six species viz., Bursa sp., Conus sp., Turris sp., Tibia sp., Natica sp., and Murex sp. Bursa sp., made major contribution to the similarity in 50 m, Murex sp. in 100 m and Strombus sp.in 200 m. Tibia sps made the largest contribution to the dissimilarity between 50 m and 100 m depth zone in between groups analysis, while Strombus sp. contributed to the difference between 100 and 200 m depth zones. When considering the season as factor, Bursa sp., Murex sp., and Tonna sp., makes the major contribution to similarity between premonsoon, postmonsoon and monsoon respectively. Dissimilarity between premonsoon and postmonsoon is contributed by Turris sps, while Tonna sps contributes to dissimilarity between premonsoon and monsoon season and Tibia sp., contributed to post monsoon and monsoon season.