Fisheries Management Strategies Research Articles

Summer diet and feeding strategy of Pacific cod (Gadus macrocephalus) inhabiting the southern coast of Hokkaido, Japan

ABSTRACT The ontogenetic and interannual variations in the diet and feeding strategy of Pacific cod (Gadus macrocephalus) were examined based on 1302 specimens collected by a trawling net off the southern coast of Hokkaido from late June to early July during 2016–2020. The diet comprised 63 species (13 taxa). Fish was the most important prey, followed by decapod crustaceans. In 2016, walleye pollock (Gadus chalcogrammus) was the dominant fish prey species, while amphipods, decapods and Japanese lanternfish (Notoscopelus japonicus) were prominent in the diet in 2017. Japanese sardine (Sardinops melanostictus) were more predominant during 2018–2020. An ontogenetic comparison of diet indicated that smaller individuals (≤400 mm standard length, SL) preyed mainly on small prey items, such as decapod crustaceans and polychaetes, whereas larger individuals (>400 mm SL) preyed mainly on fish. Moreover, prey size exhibited a significant increasing trend with predator body length. These results suggest that Pacific cod has a flexible feeding strategy that differs by life stage. The updated information on predator–prey relationships provided herein improves our understanding of energy flow in the marine ecosystem and could facilitate ecosystem-based fishery management strategies.

Population structure and low genetic diversity in the threatened lebranche Mugil liza in the Colombian Caribbean

The lebranche (Mugil liza) is an important commercial fishing species distributed throughout the Colombian Caribbean. However, overfishing and environmental damage are two factors that have significantly contributed to the reduction of its abundance, and there is no knowledge of the number of existing populations to implement the fishery management strategies. Therefore, based on nine microsatellite loci, we evaluated the genetic diversity (Ho and He), the structure (Fis, Fst, AMOVA, DAPC, and Bayesian analysis), and the population connectivity (assignment analysis) of M. liza with samples collected from eight localities distributed along the coastline of the Colombian Caribbean, including four Protected Marine Areas (MPAs). Results indicated low genetic diversity (Ho = 0.351 ± 0.040) and high inbreeding (Fis = 0.572 ± 0.041) with all loci evaluated. However, these results contrasted when the loci with the presence of null alleles were excluded (Ho = 0.592 ± 0.082; Fis = 0.289 ± 0.069). There is evidence of two populations (population 1: Santuario de Fauna y Flora el Corchal (MPA SFFC) and Vía Parque Isla Salamanca (MPA VIPIS); and population 2: the rest of the localities), that did not show a clear relationship with geographic distribution. The role of MPAs and the results of this study in management and conservation plans for M. liza in Colombia are discussed.

EDNA metabarcoding of decapod crustaceans across Indonesian seas has implications for biodiversity conservation and fisheries sustainability

Environmental DNA (eDNA) methods are increasingly viewed as alternate or complementary approaches to conventional capture-based surveys for marine conservation and fisheries management purposes, especially at large spatial scales in mega-biodiversity regions such as Indonesia. Decapod crustacean distribution and diversity across Indonesia are still poorly known, even for economically important fisheries commodities. This study assessed coral reef associated decapod diversity and distribution by sampling 40 sites in three regions (West, Central, East), representing 17 provinces and 10 Fisheries Management Areas (FMAs) across Indonesia, with a special focus on the blue swimming crab Portunus pelagicus. DNA sequencing (Illumina iSeq100) data were analysed in mBRAVE (Multiplex Barcode Research And Visualization Environment) yielded 406 OTUs belonging to 32 families, with 47 genera and 51 species identified. The number of families identified was highest in the Central region (25), while the most genera (31) and species (36) were identified in the West region. Alpha diversity did not differ significantly between regions or provinces, while Beta diversity differed significantly between provinces but not between regions. Our results also showed 31 species are possibility native based on the distribution meanwhile 12 species do not appear to have been recorded based of SeaLifeBase or WorMS. While providing a reference for further exploration of Indonesian coastal and small island decapod biodiversity, the high proportion of unidentified taxa calls for concerted efforts to develop and maintain reference specimen and sequence repositories and expand species conservation status assessments. The economically important decapod crustaceans identified in this study included three crabs (Charybdis anisodon, Charybdis japonica, Portunus pelagicus), a freshwater prawn (Macrobrachium nipponense), a lobster (Panulirus stimpsoni) and two penaeid shrimps (Mierspenaeopsis hardwickii and Trachysalambria aspera). For most decapod taxa, observed patterns indicate management under existing provincial and/or FMA level management structures is appropriate. Furthermore, the data can inform science-based fisheries management strategies, in particular for P. pelagicus.

Remote sensing modeling of environmental influences on lake fish resources by machine learning: A practice in the largest freshwater lake of China

Climate change and human interference pose a significant threat to fishery habitats and fish biodiversity, leading to changes in fishery resources. However, the impact of environmental change on lake fishery resources has been largely blurred in assessments due to the complicated variables of the lake environment. Here, taking the largest freshwater lake (Poyang Lake) in China as a study case, we first proposed a conceptual model and simulated the effect of environmental variables on fish catches based on remote sensing techniques and machine learning algorithms. We found that the hydrometeorological conditions of fishery habitats are critical controlling factors affecting the fish catches in Poyang Lake through a long time series of simulations. Among the involved hydrometeorological variables, the temperature, precipitation, and water level are strongly correlated with the fish catches in the simulation experiments. Furthermore, we tested other experiments and found that the integration with water quality variables (correlation coefficient (R) increased by 11%, and root mean square error (RMSE) decreased by 2,600 tons) and water ecological variables (R increased by 17%, and RMSE decreased by 3,200 tons) can further improve the accuracy of fish catch simulation. The results also showed that fish catches of aquatic species in Poyang Lake are more susceptible to water ecological variables than water quality refers to the model performance improvements by different input variable selections. In addition, a multi-dimension variable combination involving hydrometeorological conditions, water quality, and water ecological variables derived from remote sensing can maximally optimize the model performance of fish catch simulation (R increased by 21%, and RMSE decreased by 4,300 tons). The approach developed in this study can save the labor and financial costs for large-area investigation and the assessment of lake fishery resources compared to conventional methods. It is expected to demonstrate an efficient way for public authorities, stakeholders, and decision-makers to guide fishery conservation and management strategies.

Growth, reproduction, and feeding habits of striped bonito, Sarda orientalis, in the East China Sea

We evaluated the growth, reproduction, and feeding habits of striped bonito (Sarda orientalis) in the East China Sea. We collected a total of 289 specimens and determined their age from polished otoliths. The estimated growth function was FLt=586.98{1−exp[−0.76exp(t+0.33)]}, where FLt represents fork length (mm) at age t. Males reached spermiation in April through September, and females spawned in May through July. The main spawning periods for females were May and June. The smallest sexually mature female and male reached 445 and 436 mm in FL, respectively, and were both age 1. The principal prey species were jack mackerel (Trachurus japonicus), scad (genus Decapterus), and anchovy (Engraulis japonicus). The mean carbon and nitrogen stable isotope ratios of the striped bonito were −16.6‰ and 13.7‰, respectively. The relative contribution of prey species based on stable isotope ratios indicates that the striped bonito is an opportunistic feeder of small pelagic fishes. These biological and ecological data on the striped bonito will be of great importance for stock assessment and the development of ecosystem-based fisheries management schemes.

Anthropause shows differential influence of tourism and a no‐take reserve on the abundance and size of two fished species

Abstract Marine reserves are essential spatial conservation tools that have been shown to work alongside fishery management strategies to provide benefits to ecosystems and communities. Reserves often incentivize local tourism, which can provide the impetus for reserve creation but may have negative impacts on the ecosystem. The COVID‐19 pandemic paused global travel and provided an unprecedented opportunity to compare short‐term changes in exploited populations, during the reprieve from visitation provided by this ‘anthropause’, with the results of long‐term conservation management. Repeated surveys of Caribbean spiny lobster and Nassau grouper were conducted at popular dive and snorkel locations within a Bahamian no‐take reserve and surrounding areas during peak visitation prior to travel restrictions and immediately after restrictions were lifted. Repeated survey results were referenced against surveys over a broader area, including another Bahamian Bank, to examine the consistency of effects and how the ease of access for fishers impacted abundance. In the reserve, lobsters were encountered in significantly greater abundances, and significantly greater sizes of both lobster and grouper were observed in repeated surveys. Significantly more grouper were encountered during the repeated survey within the reserve after travel restrictions, but lobster abundances did not change significantly. Over a broader scale, lobster abundance was significantly greater further from population centres. Observed lobster abundance was affected by habitat and inferred fishing pressure, whereas observed grouper abundance was affected by survey depth, effort, and habitat. Marine reserves had clear benefits for both species and likely facilitated an increase in grouper abundance during the anthropause. Lobsters are a sustainably managed stock in The Bahamas, whereas grouper are a threatened species that appear to have benefited from an unplanned fishery restriction. Well‐managed marine reserves enhance populations long term and can have additive effects with fisheries management over short timescales.

Engagement in a Citizen Science Project in the Amazon Basin

Citizen science is a growing field that has the potential to better integrate citizens’ demands and concerns into research projects through participatory methods, and its approach can contribute to large-scale monitoring projects. In this case study article, we share and discuss methods used to promote participant engagement in a pilot initiative of the Citizen Science for the Amazon Project (CSAP). The overall project collects information on fisheries through an app and its upload tool. The pilot initiative was implemented in the main stem area of the Amazon River in Brazil from 2018 to 2019. We worked with 26 target groups, engaging participants in sessions to use and evaluate the app. Participants are residents of local communities, riverine people (ribeirinhos), with rich knowledge of natural resources and with specific conservation concerns. Fishing is an important source of income and nutrition, and fishery management strategies are a way to access and strengthen land rights. Engaging local communities in citizen science requires specific approaches to promote dialogue between different types of knowledge systems. We present an overview of our participatory strategies and use qualitative data from our monitoring to analyze outcomes. Our key recommendations include: recognizing traditional knowledge holders, including local interests, and upgrading tools according to these interests; using communication strategies to promote equitable dialogues; and stimulating and fostering networks between citizen scientists. By sharing this experience, we aim to contribute to future citizen science projects, especially in rural areas in the Global South.

Fisheries genomics of snapper (Chrysophrys auratus) along the west Australian coast.

The efficacy of fisheries management strategies depends on stock assessment and management actions being carried out at appropriate spatial scales. This requires understanding of spatial and temporal population structure and connectivity, which is challenging in weakly structured and highly connected marine populations. We carried out a population genomics study of the heavily exploited snapper (Chrysophrys auratus) along ~2600 km of the Australian coastline, with a focus on Western Australia (WA). We used 10,903 filtered SNPs in 341 individuals from eight sampling locations to characterize population structure and connectivity in snapper across WA and to assess if current spatial scales of stock assessment and management agree with evidence from population genomics. Our dataset also enabled us to investigate temporal stability in population structure as well as connectivity between WA and its nearest, eastern jurisdictional neighbour. As expected for a species influenced by the extensive ocean boundary current in the region, low genetic differentiation and high connectivity were uncovered across WA. However, we did detect strong isolation by distance and genetic discontinuities in the mid‐west and south‐east. The discontinuities correlate with boundaries between biogeographic regions, influenced by on‐shelf oceanography, and the sites of important spawning aggregations. We also detected temporal instability in genetic structure at one of our sites, possibly due to interannual variability in recruitment in adjacent regions. Our results partly contrast with the current spatial management of snapper in WA, indicating the likely benefits of a review. This study supports the value of population genomic surveys in informing the management of weakly structured and wide‐ranging marine fishery resources.

Effects of spawning success and rearing-environment on genome-wide variation of red drum in a large stock-enhancement program

Stock enhancement is an increasingly popular fisheries management strategy in which high mortality of early life history stages is circumvented by rearing juveniles in controlled or semi-controlled conditions. While the success of such programs is generally measured by the number of stocked individuals or individuals recruiting to the wild populations, an important consideration is minimizing impacts to the genetic diversity of wild populations by maximizing the number of breeders contributing to stocked progeny. The contribution of individual breeders is impacted both by variance in spawning success among adults and variance in mortality among families during grow-out. To disentangle the effects that these sources of variance have on parental contribution, red drum broodfish participating in three spawning events at the TWPD Marine Development Center were genotyped at several thousand SNP-containing loci along with their progeny. Progeny were sampled at three time points; shortly after introduction to grow-out ponds (T1), approximately midway through grow-out (T2), and as fingerlings during harvesting to be stocked in bays (T3). Using composite genotypes, progeny were assigned to parents to determine the reproductive success of individual broodfish at T1, T2, and T3 and to identify changes in the effective number of breeders (Nb) during rearing in grow-out ponds. Relationships between reproductive success and broodfish-specific parameters, including age and condition when introduced to the hatchery, time spent in the hatchery, and estimated age at spawning were assessed. Finally, associations between components of genomic variation in progeny from each sampling period and environmental parameters including salinity, pH, temperature, and dissolved oxygen present in the grow-out ponds, were identified. The results indicate that initial variance in reproductive success, including the failure of some individuals to spawn successfully, has the greatest impact on Nb. Mortality during growth had a relatively small impact on Nb and, in some cases, led to increases in Nb. Further, both family and environmental conditions in the outdoor rearing ponds significantly shaped the genetic diversity of stocked yearlings. Overall, these findings indicate that outdoor rearing in a semi-controlled environment exposes progeny to a range of environmental conditions across the season, which appears to play a role in maintaining and sometimes increasing Nb.

Assessing the role of supplementation stocking: A perspective

AbstractAlthough it is widely accepted that stocking hatchery‐cultured fish can increase the number of fish, decades of scientific evidence have shown that most often those stocking efforts fail to provide the desired “demographic boost” to a naturally reproducing, self‐sustaining target population. Despite this evidence, fish stocking remains a mainstay of fisheries management programmes, even as the biodiversity of wild fish populations and other aquatic organisms are at serious risk due to habitat loss and/or overexploitation across the globe. In this perspective piece, we summarise the reasons why wild and hatchery‐produced fish are not equivalent and describe the genetic and ecological risks associated with stocking programmes. We then present our perspective on the institutional changes that need to occur to assess these risks and offer ways to transition fisheries management strategies to become more effective in conserving levels of aquatic biodiversity from populations to landscapes. We propose that a critical first step to control ill‐conceived fish stocking programmes is to have each country develop, implement, and enforce a scientifically sound National Fish Stocking Policy. To achieve the long‐term sustainability of native fish populations, it is imperative that ecological and evolutionary principles be better integrated into future conservation strategies and management actions.

Revealing the Effectiveness of Fisheries Policy: A Biological Observation of Species Johnius belengerii in Xiamen Bay

The rapid development of China’s economy has brought tremendous pressure to the marine ecosystem, and about 57% of marine fish populations have been overexploited or collapsed. A series of fisheries policies have been implemented successively to improve the decline of resources. Over the past decade, the fisheries sector has particularly increased focus on resource and ecosystem sustainability, which has led to the wider use of stock management policies in China. Therefore, fishery resource assessment is crucial, such as assessing the long-term changes in biological information. This study is based on biological characteristics of Johnius belengerii captured by bottom trawls in Xiamen Bay during two periods, beginning in 2006 and 2016. Length composition, length–weight relationship, growth, mortality, sexual maturation, and feeding intensity were analyzed. The changes in biological characteristics show that there is a phenomenon of improvement in the later period, of which the changes are closely related to a series of fisheries management strategies, such as setting closed fishing periods and non-fishing areas, and establishing fishery restoration marine protected areas. This result seems to reveal the effectiveness of a long-term series of fisheries policies. It can provide an important basis and visibility for management effectiveness.

Age validation and growth in an exploited but poorly studied tropical fish species, the horse-eye jack (Caranx latus)

In this study, we investigated the size-at-age structure and growth of the horse-eye jack (Caranx latus), a highly mobile neritic species with significant commercial value in many parts of the tropical southwest Atlantic. For this, we combined size (standard length – SL) data and otolith readings from 282 juvenile and adult specimens of the species captured across a range of inshore (estuaries) and offshore habitats spread along the Brazilian coast between 2017 and 2019. Both otolith edge-type interpretation and marginal-increment width analysis suggested that annuli are deposited only once a year for C. latus in this part of the world, the opaque band being formed between May and August. The growth parameters estimated by the growth model that fitted best our size-at-age data (von Bertalanffy) were 782.37 mm for Linf, 0.179 for k and − 0.436 years for t0. Interestingly, fish ages differed between local inshore and offshore habitats: 91.8% of the individuals captured in the estuaries (36–223 mm SL) were age-0 fish, while all age groups (0–13 years) were found in the offshore marine area, where sizes ranged from 155 to 760 mm SL. Growth is apparently the fastest in the first year of life, allowing to reach up to 22.75% of the local maximum size expected for the species at one year. These results can inform fishery and ecosystem management strategies in Brazil but also elsewhere, as the present study provides the first assessment of C. latus growth in the South-Western Atlantic based on detailed size-at-age data for most life stages and lifetime habitats.

Resist‐accept‐direct (RAD) considerations for climate change adaptation in fisheries: The Wisconsin experience

AbstractDecision‐makers in inland fisheries management must balance ecologically and socially palatable objectives for ecosystem services within financial or physical constraints. Climate change has transformed the potential range of ecosystem services available. The Resist‐Accept‐Direct (RAD) framework offers a foundation for responding to climate‐induced ecosystem modification; however, ecosystem trajectories and current practices must be understood to improve future decisions. Using Wisconsin's diverse inland fisheries as a case study, management strategies for recreational and subsistence fisheries in response to climate change were reviewed within the RAD framework. Current strategies largely focus on resist actions, while future strategies may need to shift toward accept or direct actions. A participatory adaptive management framework and co‐production of policies between state and tribal agencies could prioritise lakes for appropriate management action, with the goal of providing a landscape of diverse fishing opportunities. This knowledge co‐production represents a process of social learning requiring substantial investments of funding and time.

Short Communication: Genetic variation of oceanic manta ray (Mobula birostris) based on mtDNA data in the Savu Sea, Indonesia

Abstract. Malik MDA, Putra MIH, Topan E, Pertiwi NPD, Artiningsih EY, Sari SK, Lewis S, Prabuning D, Sembiring A. 2022. Short Communication: Genetic variation of oceanic manta ray (Mobula birostris) based on mtDNA data in the Savu Sea, Indonesia. Biodiversitas 23: 1700-1706. The Savu Sea, one of Indonesia's top conservation priorities, is home to various marine charismatic species, including the oceanic manta ray (Mobula birostris), whose conservation status is currently endangered and is protected by the Indonesian government. However, due to domestic and global demand for its fishery products, as well as shortcomings in fisheries management, this species is still poached and bycaught in the Savu Sea. Understanding their population structure is important to achieve effective conservation and fisheries management strategies that will have a positive impact on preserving their population in this area. This study aims to reveal the genetic variation of oceanic manta rays in the Savu Sea. Thirty samples from three locations in the Savu Sea were successfully preserved from East Flores (24), West Manggarai (4), and Rote Ndao (2) and then analyzed using ND5 locus from Mithocondiral DNA (mtDNA). The result indicated a close genetic relationship between three locations (East Flores, West Manggarai, and Rote Ndao) based on the phylogenetic tree and Analysis of Molecular Variance (AMOVA) result with value of 0.05158 (P-value = 0.62268) indicated as a single population. In conclusion, the findings of this study provide some insight into the possibility of manta ray populations in the Savu Sea having strong connectivity between areas, which is critical information for regulators and managers to integrate conservation and management strategies within the Savu Sea.

Molecular phylogenetic and morphometric analysis of population structure and demography of endangered threadfin fish Eleutheronema from Indo-Pacific waters

The threadfin Eleutheronema are the important fishery resources in Indo-Pacific regions and classified as the endangered species with considerable conservation values. Their genetic diversity and population structure remain essentially unknown but are critical for the proper management and sustainable harvests of such important fisheries. Here, the mitochondrial DNA sequences of CO1 and 16s rRNA were determined from 75 individuals of Eleutheronema tetradactylum and 89 individuals of Eleutheronema rhadinum collected from different locations of South China Sea and Thailand coastal waters. Genetic diversity analysis revealed that both E. tetradactylum (Haplotype diversity, H = 0.105–0.211; Nucleotide diversity, π = 0.00017–0.00043) and E. rhadinum (H = 0.074–0.663, π = 0.00013–0.01088) had low diversity. Population structure analysis demonstrated the shallow genetic differentiation among the South China Sea populations. The limited communication between China and Thailand populations caused the high genetic differentiation in all groups due to the low dispersal ability. Reconstruction of CO1 phylogenetic relationships and demographic studies across Indo-West-Pacific regions provided strong evidence for a shared common origin or ancestor of E. tetradactylum and E. rhadinum. Eleutheronema rhadinum were further subdivided into two distinct genetic lineages, with Clade A dominantly distributing in Thailand and Malaysia and Clade B distributing in China coastal waters. Phenotypic divergence, characterized mainly by the depth of caudal peduncle and length of caudal peduncle, was also observed for all populations, which was possibly associated with specific local adaptations to environmental changes. Our study suggested a strong need for the development of proper fishery management strategies and conservation actions for the imperiled Eleutheronema species.

Population analysis of smallmouth silverside, Chirostoma chapalae Jordan & Snyder, 1899 (Atherinopsidae), an endemic fish in Lake Chapala, Mexico

Abstract A sample was analyzed of 1,129 specimens of Chirostoma chapalae from Lake Chapala, Mexico obtained from catches of local fishers between October 2016 and September 2017. Size frequency, length-weight relationships (LWRs), growth, mortality, exploitation rate, survival rate, and relative condition index were estimated. The LWRs showed negative allometric growth in females (b = 2.735) and isometric growth in males (b = 3.000). The SL∞ was 9.20 cm in females and 8.94 cm in males, and the growth coefficient k ranged from 1.80 year−1 to 1.90 year−1, and the t0 from 0.119 to 0.113. Estimated total mortality (Z = 3.20 year−1), natural mortality (M = 1.56 year−1), and fishing mortality (F = 1.64 year−1) values were higher in females. C. chapalae is at optimum, underexploited levels according to the exploitation rate (E = 0.42 year−1). The SL at first capture (SLpc) was 65.8 mm and the SL at retention (SLpr) of the fishing gear was 62.4 mm. This indicates that more than 50% of the fish caught enter the fishery at a larger size. The condition factor (Kn) showed body robustness in fall and subsequent spawning from spring onwards. Our findings contribute to the future development of fisheries management strategies in the largest lake in Mexico.

Modeling Atlantic sea scallop (Placopecten magellanicus) scope for growth on the Northeast U.S. Shelf

AbstractAtlantic sea scallops support one of the most valuable fisheries in the eastern United States. The scallop population is susceptible to climate‐related environmental stress. Assessing and projecting climate impacts rely on the fundamental understanding of scallop ecophysiology, including the influences of temperature and food supply on its energy balance and growth potential. In this study, we developed a scope for growth (SFG) model driven by high‐resolution hydrodynamic and biological models to assess the spatial and seasonal variability of scallop energy dynamics. The overall SFG on the Northeast U.S. Shelf is higher in May–June and lower in January–February, with substantial spatial heterogeneity. In the Mid‐Atlantic Bight (MAB), negative SFG occurs from July to October due to strong thermal stress. Particulate organic matter in detrital form is an important food source for scallops, with higher/lower contribution in the cold/warm seasons, respectively. Warming and food deficiency induce a noticeable contraction of suitable scallop habitats in the MAB, while their impacts on Georges Bank are insignificant. Known seasonal spawning patterns and observed growth rates in these regions match the patterns of SFG generated by the model. The sensitivity of SFG to the variations in food and temperature increases with scallop size. Large scallops are more likely to experience low or negative SFGs than smaller ones, implying that the habitats shrink as scallops grow older/bigger. This study provides key information about scallop growth potential and biogeography from the perspective of energy balance, thus helping the development of adaptive fisheries management strategies.

Reproductive cycle of the golden carpet shell (Polititapes aureus) in the Ria Formosa lagoon (southern Portugal)

AbstractThe present study described the gametogenesis and assessed the pattern of energy storage throughout the reproductive cycle of the golden carpet shell (Polititapes aureus) from the Ria Formosa lagoon (southern Portugal). Monthly sampling was performed for two years (March 2016–February 2018) and the study was based on gonad histology, complemented by the estimation of the mean gonadal index, body condition index and biochemical composition. The species’ reproductive cycle presented a seasonal pattern, with a resting period mainly between October and January and gametogenesis beginning around February–March. The spawning season of P. aureus was shorter in 2016 (June–September) than in 2017 (May–October). Furthermore, ripe individuals were very scarce (1.3%) in 2017 compared with the previous year (11.4%). Mean gonadal index (GI) reflected the species’ reproductive cycle and the body condition index (CI) and biochemical composition of the individuals exhibited high variation between years. Regarding the biochemical composition, proteins ranged between 190.6 and 595.2 μg mg−1, glycogen from 5.7 to 102.6 μg mg−1 and total lipids between 31.6 and 80.7 μg mg−1. The reproduction of P. aureus was strongly influenced by fluctuations in both seawater temperature and chlorophyll a, as reflected through the temporal variation in the gonadal cycle, condition index and biochemical composition. Overall, the information gathered in this study is valuable to propose scientifically based harvesting management measures for the long-term sustainable exploitation of this shellfish resource, further reinforcing the importance of implementing adaptive fishery management strategies to cope with global climate change.

Effect of soaking time on targets and bycatch species catch rates in fish and crab trap fishery in the southern East China Sea

Management strategies for trap fisheries in the Taiwan Strait (TS) lack crucial information such as factors determining the catch rates and bycatch species as well as the effect of the soaking time (SKT) of traps. Therefore, we investigated logbook and voyage data recorder data from Taiwanese crab and fish trap vessels (2011–2016). The crab traps were distributed widely in the TS, whereas the fish traps were mostly used in the northeast and southwest of the TS. Hierarchical cluster analysis revealed that the TS could be divided into the Northern Taiwan Strait, where most fishers use crab traps to target Portunus sanguinolentus, P. pelagicus, and Charybdis feriatus; Kuroshio Current, with large catches of Dentex hypselosomus using fish traps; and Taiwan Bank, with large catches of Evynnis cardinalis and other species using both traps. The optimal target species catch rates were achieved for a SKT of 48 h, regardless of the trap type. The bycatch rates were found to be higher when the SKT was longer than 48 h for crab traps, whereas the bycatch rates for fish traps were unaffected by the SKT. These findings may aid the implementation of sustainable trap fishing through harvest strategy planning, spatiotemporal management, and bycatch reduction.

Population parameters and sustainable status of lompa fish Thryssa baelama (Forsskal, 1775) manage through sasi approach at Haruku Village

The harvesting season of lompa fish, Thryssa baelama, through sasi, indigenous knowledge in resources management, in Haruku Village has become a socio-cultural event that attracts many people. The sasi of lompa fish has been conducted for hundreds of years. Information on the bioecology aspect of lompa fish is limited, while this information is crucial for lompa fish sustainability through the sasi approach. This study aimed to investigate some population parameters of lompa fish, its sustainability status, and proposed a sustainable management strategy for the lompa fishery of Haruku Village. Fish population parameter covers length-weight relationship, growth pattern, size distribution, sex ratio, and the body condition index. The sustainability status was assessed following the Rapfish approach. Fisheries management strategy was performed using a conceptual model framework based on Driver Pressure State Impact Response. The research shows that the total length varies between 9.2–14.3 cm. A high relationship was found between total length and weight, and the growth pattern was an allometric negative. There was a difference in sex ratio between males and females, with females dominant. The body condition index varies over time, probably due to reproductive status. The overall sustainability status was at fair condition (61.60%), with the ecological domain having the highest sustainable status (71.07%) and considered sustain. In comparison, the technological domain had the lowest sustainability status (52.58%) and was considered fair sustain. There were seven management strategies proposed for sustainable management for the lompa fishery.