4.3 Management implication
In China, approximately 50% of China’s fish stocks have been
overexploited or collapsed (Cao et al. 2017). Our approach can provide
insight in anticipation of stock enhancement and management that may
facilitate conservation and re-stocking. While our results highlight
that, as well as the previously described ‘lack of timely, effective or
sufficient management, combined with heavy fishing pressure,
particularly at spawning and overwintering grounds were major factors
responsible for croaker stock declines’ (Liu and de Mitcheson 2008),
climate change-induced overwintering habitat is another potential reason
for the stock depletion. This is highly worrying because long-lived
migratory fish like L.corcea decline even faster where both
heavily fishing and climate-induced habitat suitability synergies
(Färber et al. 2018).
The severe situation has led to an urgent need to re-evaluate fishery
management and calls for a species-specific or life-history-based
approach to stock enhancement (Young et al. 2006, Lotze et al. 2011,
Pinsky et al. 2018, Dubik et al. 2019). First, regarding the
fishing-caused size truncation effects, the deficiencies in China’s
input control allow fishers to conduct indiscriminate intense fishing on
large individuals of long-lived species after seasonal closure, and
consequently alter the dynamics of the harvested species and the
ecosystem(Shen and Heino 2014, Su et al. 2020). Hence, if capture
fishery activities are not fully regulated in a scientific and
deliberate way, restocking of long-lived migratory fish will be
difficult. Here, we suggest establishing stricter input controls on
fishery, including reducing the fishing capacity and efforts,
eliminating unregistered/illegal fishing vessels, increasing the minimum
mesh-size standard and adopting output controls, especially for
single-species total allowable catch (TAC) or/and ecosystem TAC ofL. crocea -like species. Secondly, regarding the climate-induced
overwintering habitat, we recommend designing seasonal special reserve
zones and more targeted regulations in crucial L. croceahabitats, which should be managed like MPAs. Ultimately, our application
of HSI model illuminates the mechanisms of fishing-induced life-history
variation and climate change-caused ‘mismatch’ impacts on long-lived
migratory species (Wilson et al. 2008). Also, fishery managers often
deploy hatchery release to address the recruitment bottleneck of
species’ restocking (Myers et al. 2004, Taylor et al. 2017, Kitada
2018). Because L. crocea ’s suitable overwintering habitats have
shifted towards offshore areas, to tackle both recruitment and habitat
bottleneck, we recommend that stakeholders choose larger juveniles, even
mega-spawner for hatchery release to keep pace with the shifting of
suitable habitats caused by climate change.