Movement and juvenile recruitment of mangrove jack, Lutjanus argentimaculatus (Forsskål), in northern Australia

Abstract

Lutjanus argentimaculatus, tagged and released in coastal rivers and estuaries, were found to have made inter- and intra-riverine, coastal and offshore movements. A small proportion of the recaptures made offshore movements to reef habitats of up to 315 km and these recaptures were fish that were at liberty, on average, more than twice as long as those fish that had made intra-riverine movements. Most juvenile fish <400-mm length to caudal fork (LCF) resident in rivers were recaptured less than a kilometre from where they were released. The proportion of fish making sizeable movements increased with increasing recapture size, with about of 20% of larger fish (400–500-mm LCF) making offshore, inter-riverine or coastal movements. Larger fish were primarily caught offshore, whereas smaller fish <~338-mm LCF were exclusively caught in estuarine and freshwater habitats. Recruitment of juveniles into estuarine and lower freshwater riverine habitats occurred from about February. There was temporal variability of recruitment of mangrove jack into some river systems and their relative abundance within the river system was inversely proportional to the distance from the sea. Overfishing of juveniles when they are concentrated in inshore areas could have adverse implications for mangrove jack stocks.

Reproductive biology of mangrove jack (Lutjanus argentimacuiatus) in northeastern Queensland, Australia

“…There was strong evidence that mangrove jack, throughout their Australian range, have a biphasic life cycle with immature fish occupying mostly inshore habitats and mature fish predominantly found offshore (Johannes 1978;Thollot et al 1990;Sheaves 1995;Russell & McDougall 2005). In contrast to inshore areas, a high proportion of fish sampled in our study from offshore areas were reproductively active, suggesting that most spawning occurs offshore.…”

“…In the current study, only a small number of the fish sampled either from estuaries or in fresh water were found to be mature or maturing, but their presence suggests that there is limited potential for spawning in these areas. Russell & McDougall (2005) provided strong evidence of unidirectional, offshore movements of L. argentimaculatus from rivers and coastal areas. Sheaves (1995) reasoned that the lack of large, old, reproductively active individuals inshore supported the contention that, after migrating offshore, adults do not return to estuaries.…”

“…In Tanzania, Kamukuru et al (2005) suggest that limited protection provided by a marine park was vital for sustaining adjacent areas that were heavily fished for L. fiilviflamma. Stock assessments suggest that the fishery in eastern Queensland is not currently under pressure (Russell et al 2003), although recent targeting by trawlers of aggregations of mangrove jack in other parts of northern Australia (Jason Stapley, Queensland Department of Primary Industries and Fisheries pers. comm.)…”

“…This work was part of a larger biological study of the L. argentimaculatus fishery in northeastern Australia (Russell et al 2003).…”

Settlement behaviour of larvae of the Stripey Snapper, Lutjanus carponotatus (Teleostei: Lutjanidae)

“…Some species of coral-reef dwelling Lutjanus settle into seagrass or mangrove habitats (Dorenbosch et al 2004;Russell and McDougall 2005;Nakamura et al 2006;Pollux et al 2007), others into isolated coral heads within sea grasses (Nanami and Yamada 2009), both followed by ontogenetic, postsettlement migration to reef habitat. Direct settlement onto reefs has been reported in other Lutjanus species (Sweatman 1993;Lecchini and Galzin 2005).…”