Variations in otolith patterns, sizes and body morphometrics of jack mackerel Trachurus japonicus juveniles
Abstract:Variations in otolith patterns, sizes and body morphometrics of jack mackerel Trachurus japonicus juveniles were investigated. Under transmitted light, translucent (Wt) and opaque otoliths (Wo) were detected in juveniles collected from Wakasa Bay between July 2005 and April 2006, whereas only opaque otoliths (Go) were detected in Goto-nada Sea individuals between May and June 2006. Three groups of juveniles were distinguished based on differences in hatch season, otolith size and growth history, and body morphometrics. As T. japonicus has different spawning seasons according to spawning grounds, each group was estimated to hatch in different waters. Juveniles with Wt otoliths were considered to have stayed in coastal habitat longer, as the hatch area was estimated to be near Wakasa Bay. Juveniles with Wo and Go otoliths appear to recruit to coastal waters at larger size, since their hatch areas were estimated to be far from each collection area. Larger otoliths of Wt were attributed to otolith accretion after the second growth flexion, which was observed only for Wt. Standard length of Wt fish at the second otolith growth flexion was estimated to correspond to recruitment size to coastal rocky reefs in Wakasa Bay. Body morphometrics were correlated with otolith size after removing body size effect, suggesting that morphological variations of T. japonicus juveniles were also associated with the timing of recruitment to coastal habitat.
Document Type: Regular Paper
Affiliations: 1: Nature Conservation Bureau, Ministry of the Environment, 1-2-2 Kasumigaseki, Chiyoda, Tokyo 100-8975, Japan 2: Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan 3: Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Chinese Academy of Sciences, Wuhan, Hubei 430072, China 4: Maizuru Fisheries Research Station, Kyoto University, Nagahama, Maizuru, Kyoto 625-0086, Japan 5: Seikai National Fisheries Research Institute, Fisheries Research Agency, 1551-8 Taira-machi, Nagasaki 851-2213, Japan
Publication date: 2010-10-01