Successful stocking of a depleted species, spotted halibut Verasper variegatus, in Miyako Bay, Japan: evaluation from post-release surveys and landings

Abstract

Post-release adaptation and stocking effectiveness of a highly depleted pleuronectid flatfish, spotted halibut Verasper variegatus, were assessed in Miyako Bay, Japan. In early July 2004 and 2005, 22 000 and 5000 hatchery-reared juveniles (mean 81.2 and 89.8 mm total length, respectively) were released in shallow waters in the inner bay area. Results from surveys with a 2 m beamtrawl conducted over a 2 mo post-release period, laboratory predation experiments using potential predators (age-1 Japanese flounder), and a market census continued until December 2008, suggested that released juveniles, which had a size refuge from predators, could quickly adapt to brackish water habitats where there were suitable physical conditions (temperature, salinity and sediments) and abundant prey organisms. Juveniles selectively preyed on epibenthic gammarids and cumaceans, and had full stomachs 1 wk after release. Some released fish grew to > 40 cm by age-1+, feeding exclusively on larger crustaceans (e.g. isopods, carideans and brachyurans). Market census revealed that released fish showed > 99% contribution to catches, and recapture rates for fish released in 2004 (7.6%) and 2005 (15.7%) were higher than for releases in 2000 to 2003 (0.7 to 5.0%), possibly due to the development and application of improved release strategies (i.e. release habitat, size and season was appropriate in 2004 and 2005). Our study demonstrates that (1) local depleted stocks can be effectively restored by hatchery releases and that (2) development of release strategies based on the analysis of ecological interactions between released juveniles and the target ecosystem can largely contribute to the successful restocking of depleted species.

Post‐release feeding and growth of hatchery‐reared Japanese flounder Paralichthys olivaceus: relevance to stocking effectiveness

“…The two‐piece regressions often detect the decrease in L T in the first piece, possibly because of the sampling bias from the laboratory (0 DAR) and from the field (after release). Additionally, a decrease or increase in the body size of collected individuals after release might occur because of the dispersal of larger individuals (Wada et al , 2010) or because of lower survival in smaller individuals (Yamashita et al , 1994; Leber, 1995). Estimation of post‐release growth using other methods such as otolith microstructure analysis or tag‐recapture experiments could elucidate the changes in growth rates associated with adaptation to natural environments.…”

“…1 week) and reduces stocking effectiveness. To achieve greater survival of released fishes, release strategies such as the selection of release sites and seasons (Fairchild et al , 2005; Tanaka et al , 2006; Wada et al , 2010) as well as size at release (Tsukamoto et al , 1989; Yamashita et al , 1994; Leber, 1995; Tominaga & Watanabe, 1998) should be improved.…”

Sustainable fisheries management through reliable restocking and stock enhancement evaluation with environmental DNA

“…Genetic data has also been used to inform decisions on restocking and other aspects of management for unusual fish populations 14 . Nonetheless, it is difficult to claim the successful stocking of any impoverished species due to numerous obstacles, including the production of cost-effective juveniles, the development of adequate release tactics, and the availability of suitable monitoring and evaluation techniques 10 , 15 . The success of stock enhancement must be evaluated in order to maximise the potential benefits of fisheries and ensure their sustainability.…”

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“…Consequently, it has been integral to the calculation of pollution indices as at least some of its species are considered to be insensitive to pollution, unlike other amphipods (Bellan 1980;Gray et al 1990;Dauvin & Ruellet 2007;Dauvin et al 2016;de-la-Ossa-Carretero & Dauvin 2010). As a positive influence, it reduces epiphyte fouling of macroalgae and seagrasses (Duffy 1990), it consumes excess organics released from fish farms (Gonzalez-Silvera et al 2015) and it provides a food resource for gray whales (Dailey et al 2000), fish (Blankley 1982;Bennett et al 1983;Brawley & Fei 1987;Pulfrich & Griffiths 1988;Wilber et al 2003;Norderhaug et al 2005;De Troch et al 2013;Reubens et al 2010Reubens et al , 2013Reubens et al , 2014aWada et al 2010;Stenberg et al 2015;Choi et al 2017;Ventura et al 2017;Şensurat-Genç et al 2019) and invertebrates (McCain 1968;Sebens 1985;Genzano 2005;Donahue et al 2009;Di Camillo et al 2013;Caplins & Turbeville 2010). Correct identification is essential for behavioural, conservation, ecological, genetic, taxonomic and phyletic studies and for identifying introductions and their impacts (e.g., Borowsky 1985;Karez & Ludynia 2003;Krapp et al 2008Krapp et al , 2010Pilgrim & Darling 2010;Lobo et al 2017).…”