4.3 Management implication
In China, approximately 50% of China’s fish stocks have been
overexploited or collapsed (Cao et al. 2017). In response to fishery
collapse, the Chinese government has introduced comprehensive management
tools, including input controls (restriction on fishing net mesh-size,
fishing vessel numbers and horsepower, and seasonal closure policies)
and, more recently, output controls, MPAs and co-management approaches
(Shen and Heino 2014, Su et al. 2020). 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. 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.