Application of a catch-based method for stock assessment of three important fisheries in the East China Sea

Most fisheries in China do not have maximum sustainable yield（MSY） estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch（TAC） for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model.Estimates for intrinsic rate of increase（r） and five levels of process error were considered. Results showed hairtail Trichiurus japonicas（Temminck and Schlegel） and small yellow croaker Larimichthys polyactis（Bleeker） fisheries experienced overfishing from the mid-1990 s to the early 2000 s, and the suggested TACs were 55.8×10^4 t and9.06×10^4 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea（Richardson） caused the fishery＇s collapse in the 1980 s, and it has not recovered until today.The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.

Estimation of catch losses resulting from overexploitation in the global marine fisheries

Many fish stocks in the world are depleted as a result of overexploitation, which reduces stock productivity and results in loss of potential yields. In this study we analyzed the catch trends and approximate thresholds of sustainable fishing for fished stocks to estimate the potential loss of catch and revenue of global fisheries as a result of overexploitation during the period of 1950–2010 in 14 FAO fishing areas. About 35% of stocks in the global marine ocean have or had suffered from overexploitation at present. The global catch losses amounted to 332.8 million tonnes over 1950–2010, resulting in a direct economic loss of US$298.9 billion（constant 2005 US$）.Unsustainable fishing caused substantial potential losses worldwide, especially in the northern hemisphere.Estimated potential losses due to overfishing for different groups of resources showed that the low-value but abundant small-medium pelagics made the largest contribution to the global catch loss, with a weight of 265.0 million tonnes. The geographic expansion of overfishing not only showed serial depletion of world＇s fishery resources, but also reflected how recent trends towards sustainability can stabilize or reverse catch losses.Reduction of global fishing capacity and changes in fishery management systems are necessary if the long-term sustainability of marine fisheries in the world is to be achieved.

Population Structures and Diets of Two Species of <i>Pisodonophis</i>(Ophichthidae) from the Southwest Coast of Taiwan

This study was used to lift nets and trap net fishing at intertidal zone of lagoon and estuarine regions of southern Taiwan. From July 2013 to July 2018, a total 420 specimens of Pisodonophis were analyzed, the average total body length (TL) and average body weight (W) of P. boro eels are 68.4 ± 11.9 cm and 140.4 ± 86.1 g (N = 194), respectively. Typically, P. cancrivorus eels are smaller (TL = 52.8 ± 9.2 cm) and lighter (W = 107.9 ± 73.7 g [N = 119]) than P. boro eels. The natural logarithmic linear relationships between the TL and W of P. boro and P. cancrivorus are respectively expressed as ln(W)b = 2.4405 ln(TL) − 5.4448 (R2 = 0.796, N = 194) and ln(W)c = 3.2168 ln(TL) − 8.2027, (R2 = 0.934, N= 119). P. cancrivorus typically preys on shrimp, crab, and fish;lab assessment revealed that the frequencies of occurrence of these foods in their guts were 49%, 21%, and 15%, respectively (N = 100). The main catch months of P. boro were during the rainy season, and that of P. cancrivorus were the winter season in Taiwan. The average W values of P. boro from Jhuoshuei and Puzih estuaries were 343.2 ± 218.8 g (N = 91) and 140.4 ± 86.1 g (N = 194), respectively. Furthermore, the results of the study revealed that the Puzih estuary is overfished. We suggest that fishery management units should develop some protection measures for the conservation of aquatic ecosystems in estuarine regions. For example, the P. boro weighing less than 113 g will be released back to the estuary.

Community’s Perspectives towards Marine Protected Area in Perhentian Marine Park, Malaysia

The Perhentian Islands located in the East coast of Peninsular Malaysia. They are well-known for their rich coral reef ecosystems. Marine resources of Malaysia have been overexploited in general due to overfishing and other development activities. Such no-take marine protected areas (MPAs) were established in Malaysia including Perhentian Islands Marine Park to enable overexploited marine resources to recover and to conserve coral reef ecosystems. This paper examines the current level of activities causing damages to the coral reef habitats in the Perhentian MPA. This study used paired comparison method to elicit the perception of the local stakeholders on the activities harmful to the marine habitats. The results of the analysis showed that various respondent groups had similar preference rankings on the harmful activities: littering, discarding fishing equipments, excess fishing and too many divers that cause damage to the habitats in the MPA area. The findings suggest that policy makers should take cognizance of the local stakeholders’ concern in planning and designing of marine protected areas in Malaysia.

Impact of Fishing and Stocking Practices on Coregonid Diversity

Fish species diversity can be lost through interacting stressors including habitat loss, stocking and overfishing. Although a multitude of stressors have played a role in the global decline of coregonid (Coregonus spp.) diversity, a number of contemporary studies have identified habitat loss stemming from eutrophication as the primary cause. Unfortunately, reconstructing the role of fishing and stocking practices can be difficult, because these records are incomplete or appear only in hard-to-access historic grey literature. Based on an illustrative set of historic and contemporary studies, we describe how fisheries management practices may have contributed to coregonid diversity loss in European and North American lakes. We provide case studies examining how fishing and stocking may reduce coregonid diversity through demographic decline and introgressive hybridization. In some lakes, fisheries management practices may have led to a loss of coregonid diversity well before issues with habitat degradation manifested. Our review suggests that fish conservation policies could beneficially consider the relative importance of all stressors, including management practices, as potential drivers of diversity loss.

Fishing of the Flat Sardinella (Sardinella maderensis, Pisces, Lowe 1838) in Benin (West Africa) Nearshore Waters: Production, Typology of Fishing Gear and Current Status of Its Stock

Sardinella maderensis is one of the fish species well appreciated in Benin. In recent years, this species has experienced a decrease in its production in the coastal waters of this country. To search for the causes of this decline in production, a standard survey was carried out using Computed Assisted Personal Interviewing with the 38 artisanal fishermen at the artisanal fishing port of Cotonou who targets this species in order to inquire about the fishing gear and techniques of production. The current stock status of this species was determined using FiSAT from a sample of 1240 specimens collected randomly in commercial catches from January to December 2021. The typical survey revealed a massive use of non-regulatory fishing mesh gear (86.85%). The fishing effort is also sustained and results in a fishing mortality rate (F = 2.88 yr-1) higher than the rate of natural mortality (M = 2.22 yr-1) suggesting overfishing of the stock. Sustainable management through capacity building of fishermen and application of regulations in terms of gear mesh size and respect for fishing seasons could be stated.