Numbers and sizes of the shrimp Rhynchocinetes uritai Kubo, 1942 (Decapoda: Caridea) caught in bait and refuge traps

Abstract

Catch rates and sizes of hingebeak shrimp Rhynchocinetes uritai Kubo, 1942 were studied with two types of traps: bait traps that were exposed for 1-2 days and unbaited "refuge traps" exposed for 2-4 weeks. Shrimp were collected twice a month from June 2010 to May 2012 on rocky substrata in Oura Bay, Shimoda, Japan. Overall the numbers of shrimp caught did not differ between the two trap types, but when adjusted for soak times, the bait traps had substantially higher catch rates than the refuge traps. Addition of light to the bait traps had no significant effect on catch rates. However, shrimp in the baited traps were significantly larger than those in the refuge traps. The results show that size distribution can be greatly affected by trap type. Consequently, using two types of traps simultaneously increases not only the catch efficiency but also ensures that all sizes of the reproductively mature shrimp population are sampled in adequate numbers, which is especially important in protandric hermaphrodites.