Ahmadi Ahmadi
Lecturer, Faculty of Marine and Fisheries, Lambung Mangkurat University
Title: Trapping Survey for the Red Frog Crabs (Ranina Ranina) Using the Baited Tangle Nets and Pots in Offshore Tanegashima, Japan
Biography
Biography: Ahmadi Ahmadi
Abstract
In Japan, the spanner crab or the red frog crab Ranina ranina (Linnaeus, 1758), locally known as “Asahigani”, is an important edible crab for local people in Tanegashima island. We carried out trapping survey to determine the best way of catching for the crab using the baited tangle nets and pots from offshore Tanegashima. The baited tangle nets were made of PA nylon multifilament with five different mesh sizes (37.8mm, 50.5mm, 75.8mm, 97.0mm and 121.2 mm). While the pots were made of PE nylon multifilament with 15mm mesh size. Both traps were attached at 5 m intervals along the line randomly and were lowered onto the seabed for about 5-hr soak time before being taken. A total of 96 crabs R. ranina consisted of 61 males (64%) and 35 females (36%) was caught primarily with the baited tangle nets. The size frequency of males and females was ranged from 67.2 to 138.5mm and from 50.4 to 128.6mm respectively. In term of foraging behavior, males were more abundant in this area. The CPUE for the baited tangle nets was ranged from 2.8 ± 0.58 to 5.4 ± 2.41. The number of the legal-sized crabs ( 93mm) was half time higher than undersized crabs (< 93mm), and most of them were males. The use of a larger mesh size seems to prevent the crabs from further damage and is optimal with respect to clearing-time and escapement of the juvenile crab from the nets. None of R. ranina was found in the pots.