Respons Kepiting Bakau (Scylla serrata Forskal 1775) terhadap Tingkat Kebusukan Umpan Keong Emas (Pomacea canaliculata Lamarck 1822)

Abstract

Kepiting bakau (Scylla serrata Forskal 1775) dikenal sebagai pemakan segala bangkai (omnivorous-scavenger) (Ariola 1940 dan Moosa et al. 1985 dalam Mulya 2000). Kepiting bakau umumnya memangsa gastropoda, bivalve dan berbagai hewan-hewan kecil yang dapat mereka tangkap, tetapi mereka juga pemakan bangkai yang giat (vigorous scavenger) (Hill 1976). Sebagai pemakan bangkai mereka mudah tertangkap dengan trap berumpan baik dalam penangkapan komersial maupun rekreasional (Hill 2007). Kepiting bakau adalah pemakan bangkai yang rakus (voracious scavenger), yang dapat mencari dan memangsa bangkai di perairan estuarin yang keruh dan berhutan bakau. Kepiting bakau adalah pemakan bangkai oportunistik (opportunistic scavenger) (Webley 2008). Opportunistic scavenger umumnya mengadopsi strategi duduk dan menunggu (sit and wait strategy) untuk mencari bangkai (Rose dan Polis 1998 dalam Webley 2008) sehingga bangkai yang diperoleh adalah bangkai yang sudah membusuk.

Mud crab is well known as omnivorous-vigorous-voracious-opportunistic-scavenger. These intertidal animals applies mainly chemoreception in their predatory behaviour. It has been commonly assumed that non fresh gold snail bait is better than fresh bait in stimulating the mud crab. This research's aim is to analyze mud crab response to different decaying level of gold snail bait. Their response were observed as time required to touch the bait and pattern and direction of the mud crab in approaching the baits. The different decaying level of gold snail baits were shown on Total Volatile Base Nitrogen (TVBN) as 16.3 mg/100g (0 day); 534.1 mg/100g (3 days); and 887.4 mg/100g (6 days). The research was conducted from July 2009 until February 2011. The TVBN test for gold snail baits were conducted at Laboratory of BBPPHP Jakarta. The experiment was conducted in Pemalang. The result showed that the average period of mud crabs to touch the baits were 52.14 minutes; 61.57 minutes and 52.57 minutes. Anova test concluded no sufficient evidence of significant effect of TVBN content of gold snail bait on mud crab’s feeding behaviour. Movement pattern B, i.e. left and right deviation followed by straight forward movement to the bait, was commonly exhibited by the crabs. Consequences of time period required by the mud crab to approach the bait on fishing operation is discussed.