ife history of Argyrosomus japonicus , a large sciaenid at the southern art of its global distribution : Implications for fisheries management reg

The life-history of the sciaenid Argyrosomus japonicus in South Australia was investigated to inform a review of fisheries management. Validated, otolith-based growth coefficients for females (L = 1430.52, inf K = 0.137, t0 = −0.303, n = 209) and males (Linf = 1356.23, K = 0.159, t0 = 0.000, n = 185) suggested high asymptotic size and low growth rates, relative to other populations. A growth performance index (ω) was lower for A. japonicus in South Australia than for other populations. Sizes at 50 and 95% maturity (SAM ) were 850 and 1028 mm TL, respectively for females and 778 and 50,95 923 mm TL, respectively for males. Age structures from 2011 appeared truncated compared to those from 2001 and 2002 with no individuals greater than 10 years old. The dominant year class observed in age structures from 2001 and 2002 was not present in 2011. This may reflect the combined effects of historically severe drought from 2002 to 2010 and fishing. This population is vulnerable to fishing as juveniles in estuarine habitat and as adults in spawning aggregations in marine habitat. Loss of protected estuarine habitat for juveniles from flow regulation and drought may make this population particularly vulnerable to overfishing. ulloway Kob Whilst maintenance of appropriately timed freshwater inflows to estuarine habitat is important for this population their availability is uncertain. Populations of A. japonicus in South Australia would benefit from management measures that: (i) aim to preserve capacity for egg production; (ii) allow recruits to enter the adult population; and that (iii) rebuild and maintain long-tailed age structures. Amendments to the legal minimum size and the protection of juveniles in estuaries and the adult spawning/feeding aggregations are recommended. Introduction Body size of fishes is one of the most important factors in deterining vulnerability to fishing (Jennings and Kaiser, 1998; Jennings t al., 1999; Reynolds et al., 2005). Large-bodied fishes are usully long-lived and their vulnerability is evident by their loss from ulti-species catches (Ferguson et al., 2013; Winemiller and Rose, 992). The life-history of such large, long-lived fishes is often based n delayed maturity and high fecundity and has been termed ‘bet edging’ or periodic strategist (Winemiller and Rose, 1992 ) because eproductive output is allocated across many years allowing popuations to survive periods that are unfavourable for spawning and arval dispersal (Longhurst, 2002 ). For periodic strategists, recruitent of newly mature individuals is low relative to the number and iomass of older adults with the exception of occasional very strong ear classes for those species with highly variable reproductive uccess (Heppell et al., 2005). ∗ Corresponding author. Tel. : +61 8 8207 5467; fax: +61 88207 5481. E-mail address: greg.ferguson@sa.gov. au (G.J. Ferguson). 165-7836/$ – see front matter © 2013 Elsevier B.V. All rights reserved. ttp://dx.doi. org/10.1016/j.fishres. 2013.11. 002 © 2013 Elsevier B.V. All rights reserved. Many large sciaenids have “periodic strategist” life histories with characteristic high longevity and late maturity. Additionally, many sciaenids form spawning aggregations in and near estuaries and recruitment success of several species has been linked to fresh water inflows into estuaries (Cisneros-Mata et al., 1995; Griffiths, 1996; Ferguson et al., 2008; Rowell et al., 2005, 2008 ). The evolution of late maturity in sciaenids may have been facilitated by low juvenile mortality in protected estuarine and surf zone habitats (Griffiths, 1996) and a possible “river-discharge” spawning relationship (Ferguson et al., 2008). The delayed maturity of some sciaenid species may make them particularly vulnerable to overfishing (Musick, 1999; Musick et al., 2000). Recruitment overfishing resulting from the combined effects of targeting juveniles in estuaries and adults in spawning aggregations, referred to as the “one-two punch” approach (Rowell et al., 2008), has been implicated in the declines of several sciaenid species worldwide. Sciaenid populations in serious decline include five species in the west Pacific (Liu and Sadovy de Mitcheson, 2008; Sadovy and Cheung, 2003 ), one species in Europe (Quéméner, 2002 ) and seven species in North America (Musick et al., 2000). For example, estuarine dependence, slow growth rates, and high age at