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 <i>Turris</i> sps (19.7%) in 51-100 m and <i>Conus sp</i>. 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., <i style="mso-bidi-font-style:normal">Bursa</i> sp., <i style="mso-bidi-font-style:normal">Conus </i>sp., <i style="mso-bidi-font-style: normal">Turris</i> sp., <i style="mso-bidi-font-style:normal">Tibia</i> sp., <i style="mso-bidi-font-style:normal">Natica </i>sp., and <i style="mso-bidi-font-style: normal">Murex</i> sp.<i style="mso-bidi-font-style:normal"> Bursa</i> sp., made major contribution to the similarity in 50 m, <i style="mso-bidi-font-style:normal">Murex</i> sp. in 100 m and <i style="mso-bidi-font-style:normal">Strombus</i> sp.in 200 m. <i style="mso-bidi-font-style:normal">Tibia</i> sps made the largest contribution to the dissimilarity between 50 m and 100 m depth zone in between groups analysis, while <i style="mso-bidi-font-style:normal">Strombus</i> sp. contributed to the difference between 100 and 200 m depth zones. When considering the season as factor, <i style="mso-bidi-font-style:normal">Bursa</i> sp., <i style="mso-bidi-font-style:normal">Murex</i> sp., and <i style="mso-bidi-font-style:normal">Tonna</i> sp., makes the major contribution to similarity between premonsoon, postmonsoon and monsoon respectively. Dissimilarity between premonsoon and postmonsoon is contributed by <i style="mso-bidi-font-style: normal">Turris</i> sps, while <i style="mso-bidi-font-style:normal">Tonna</i> sps contributes to dissimilarity between premonsoon and monsoon season and <i style="mso-bidi-font-style:normal">Tibia</i> sp., contributed to post monsoon and monsoon season.