Abstract
The status of fishery resources in the Yangtze estuary and its adjacent waters is still unclear for the effective implementation of fishery management strategies. To help address this gap, a new method especially for data-limited fish stocks (LBB) was applied to assess seven commercially and ecotrophically important fish stocks. Fish specimens were collected in the estuary by bottom trawling quarterly from May 2018 to February 2019. Two historical datasets were collected with the same method in the same area for Indian perch (Jaydia lineata) and sickle pomfret (Pampus echinogaster). To explore the growth features and resilience of fish stocks, auximetric plots and growth performance indices (Φ′) were used. Results showed that common hairfin anchovy (Setipinna tenuifilis) in 2018 and Indian perch in 2018 showed a healthy stock biomass status with complete length structures under a sustainable fishing pressure. The others were outside of safe biological limits or overfished. The Lmean/Lopt < 0.9 in six (67%) of nine LBB models for seven fish stocks suggested that most of the stocks were truncated in length structures. This contribution provides the main fishery reference points regarding stock status that can inform managers and form the basis for various management strategies.
Highlights
Despite the fact that China has the largest capture production worldwide with the insight of the distortion in catches (Watson and Pauly, 2001; Pauly and Le Manach, 2015; FAO, 2019), effective fishery management remains a huge challenge
Nine length-based Bayesian biomass estimator (LBB) models were constructed for seven fish stocks from the YE
The Lopt dash lines indicated relatively good stock status or good length structures if they were at the middle or left of the peak of the curves (Figure 3), which implied that only three stocks had relatively good length structures in this study
Summary
Despite the fact that China has the largest capture production worldwide with the insight of the distortion in catches (Watson and Pauly, 2001; Pauly and Le Manach, 2015; FAO, 2019), effective fishery management remains a huge challenge. There are various fishery management strategies in China, including input control, output control, technical control and management. LBB Assessments for Seven Fishes measures, economic instruments, management of aquaculture, distant water fisheries management, and international cooperation mechanisms (Cao et al, 2017; Huang and Tang, 2019). The effects of these strategies regarding fishery conservation are limited. The fishery licensing system (input control) has been in force since 1979. There is a noticeable gap between reality and expectation regarding the licensing system’s implementation process because the prerequisite, namely the status of fishery resources, is often neglected (Huang and Tang, 2019). In China, such a gap along with the lack of fishery reference points and raw data precludes the possibility of optimizing management and conserving fishery resources
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