Offshore Fisheries Research Articles

A quantitative analysis of greenhouse gas emissions from the major offshore fisheries

A quantitative analysis of greenhouse gas emissions from the major offshore fisheries

Fishermen's perceptions of coastal fisheries management regulations: Key factors to rebuilding coastal fishery resources in Taiwan

Although Taiwan has taken conservation measures for coastal and offshore fishery resources in recent years, the effectiveness of resources rebuilding is unclear. Many initiatives, such as marine protected areas (MPAs), are frequently opposed by fishermen. This research reviewed management measures and interviewed 313 fishermen by purposive stratification and snowball sampling. Data were analyzed by fishery, age, and vessel size to address the attitudes and perceptions of fishermen toward twelve fisheries management measures. Descriptive statistics, as well as chi-squared tests and independent t-tests, were used for basic analysis and differences comparison between groups. The results showed that illegal fishing vessels from China (71%), overfishing (69.5%), and ghost fishing (64%) are considered as major threats to Taiwan marine resources. The measures from voyage data recorders, larval anchovy, precious coral, and shark management result in higher satisfaction because of strict monitoring. The satisfaction measures for three net-type measures, i.e., trawler area closure, torch-light limitation, and gillnet limitation, were low. Line-type and small-scale vessel fishermen are more concerned with “small mesh size” and “ghost fishing”. Net-type, large-scale vessels and young fishermen were concerned about “climate change” and “inappropriate measures”. In conclusion, the priorities are to (1) establish a comprehensive scientific research framework; (2) strengthen enforcement to ensure resources rebuilding, especially for large-scale net fisheries; (3) promote public awareness and build communication between stakeholders to obtain support; and (4) communicate among policymakers and fishermen to increase mutual understanding.

Environmental processes and ecological effects of microplastics in the ocean

There are no doubts that plastics problem in the ocean environment has become an increasingly worldwide focus in past several decades. A number of experts regard the plastic wastes as one of the hardest anthropogenic threats. The degraded items of large individual plastics lead to millions of microplstics (MPs) ultimately. As a result, the new pollution has appeared in the ocean. The ever-growing MPs have been detected in subtotal sea products, such as sea food and table salts. The MPs can bring potential health risk to people by enrichment in sea products. Furthermore, the economic development of offshore fishery and the marine tourism have been inhibited badly. This article will make a brief review on present studies about MPs in the ocean.

Discrimination of Wild and Hatchery-Reared Black Porgy <i>Acanthopagrus schlegelii</i> Using Otolith Elements Analysis of Magnesium and Manganese

Due to the decreasing resources of both inshore and offshore fisheries, many organizations have released fry to enhance their stock in recent years. The discrimination between wild and hatchery-reared individuals must be performed to assess the efficiency of the release. Fresh groundwater is generally used by hatchers in southwesternTaiwanto decrease salinity and to promote the growth of larvae prior to feeding; thus, the elemental composition of the otolith may be different in stocks, and this difference may be used for identification. This study used Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) to analyze the trace elements in the nuclei of otoliths from black porgy Acanthopagrus schlegelii, including six hatchery reared specimens from the Tainan County, three recaptured marked and ten captured unmarked specimens from the Miaoli County in Northwestern coast of Taiwan. Among the six hatchery and three recaptured marked specimens, which ranged from 4.9 to23.4 cmin body length, the nucleus zone (relative to within5 cmin size growth) of the otoliths showed higher magnesium concentrations than that observed on both edges. The distribution was similar to an inverse “V” shape. The otoliths also showed lower manganese concentrations near the nucleus and had higher values near the edges, resulting in a distribution similar to a “U” shape. According to the appeared shape of Mg2+/Ca2+ and Mn2+/Ca2+ ratio in the central area of the nucleus zone, this study determined six specimens which were from hatchery reared and three specimens were from wild among ten unmarked specimens captured from the Northwestern coast of Taiwan. Under the conditions used in this study, the absorption of calcium into the otolith was active and required energy in the seawater and freshwater, while the incorporation of magnesium and manganese was passive and was primarily affected by diffusion.

Future of Fishing for a Vulnerable Atoll: Trends in Catch and Catch-Per-Unit-Effort in Tokelau’s Domestic Marine Fisheries 1950–2016

Tokelau is among the most vulnerable countries to climate change from both an environmental and economic perspective, whilst being highly dependent on marine resources for dietary nutrition. Industrial as well as small-scale fisheries are present in Tokelau’s waters, with Tokelau itself only participating in small-scale fisheries. Industrial fisheries consist exclusively of foreign distant-water tuna fleets. This study aims to reconstruct and investigate the trends in the domestic small-scale marine fisheries catches, fishing effort, and catch-per-unit-effort (CPUE) from 1950 to 2016. We used kWdays as our metric of fishing effort or fishing capacity, estimated using length, motorization and type of fishing vessels. Total fishing effort was approximately 11,900 kWdays in 1950 and increased rapidly after the 1980s with the introduction of larger motorized vessels. Despite evolving fishing effort, catches taken in subsistence fisheries have been relatively consistent at approximately 370 t⋅year −1 , resulting in a reduction of subsistence CPUE from 32.4 kg⋅kWdays −1 in 1950 to 2.6 kg⋅kWdays −1 in 2016. This trend is opposite to that of the artisanal fishery, where CPUE increased since the start of this fishery in 2003, from 1.7 kg⋅kWdays −1 to 2.6 kg⋅kWdays −1 in 2016. Tokelau’s domestic catch is greatly underreported, with reconstructed domestic catch since 2010 being nearly four times larger than the data reported by the Food and Agriculture Organization (FAO) of the United Nations on behalf of Tokelau. The abundance of reef fishes are predicted to decrease while the abundance of pelagic fishes is expected to increase within Tokelau’s waters due to climate change, likely further altering future fishing practices. The present CPUE analysis, combined with the forecasted effects of climate change, suggests that the domestic fisheries in Tokelau may be on an unsustainable path, highlighting food security concerns, despite the potential for growth in offshore fisheries.

Comparative study of greenhouse gas emission from coastal and offshore gillnet and trap fisheries by field research

Comparative study of greenhouse gas emission from coastal and offshore gillnet and trap fisheries by field research

Optimal harvesting strategy of a stochastic inshore–offshore hairtail fishery model driven by Lévy jumps in a polluted environment

With the increasing demand for aquatic products all over the world, exploring the interactions between inshore and offshore fisheries is one of the meaningful issues to help boost yield and meet immediate protein needs. However, pollution and environmental fluctuations (fishery trading market, ocean meteorological factors) may seriously affect the optimal harvesting strategy of the interaction between inshore and offshore components of the fishery. In response to this problem, we present a stochastic inshore–offshore fishery model in a polluted environment, which incorporates harvesting efforts subjected to Levy jumps and environmental toxicant influence. By virtue of the ergodic methods, the optimal harvesting effort and maximum expectation of sustainable yields are established. Using the hairtail fisheries in the East China Sea as a case study, numerical simulations are carried out to support the theoretical results. These results show that the diffusion between inshore and offshore fisheries, Levy jumps noise and environmental toxicant input may significantly affect the optimal harvesting strategy, which can provide suggestions for effective measures to increase the aquatic products and guide harmonious development of inshore and offshore aquaculture.

Energy Consumption and Greenhouse Gas Emission of Korean Offshore Fisheries

This paper presents the energy and greenhouse gas (GHG) emission assessments of Korean offshore fisheries. The consumption of energy by fisheries is a significant concern because of its attendant environmental effect, as well as the cost of the fuel consumed in fishing industry. With the global attention of reducing GHG emission and increasing energy efficiency of fuel, the seafood industry needs to further understand its energy use and reduce its GHG emission. In the present study, the amount of energy consumed and the GHG emission of Korean offshore fisheries in a period from 2009 to 2013 were examined. Offshore fisheries accounted for 24% of Korean production in 2013 and 60% of fuel consumption related GHG emission. Whereas the total GHG emission intensity of this sector improved slightly between 2009 and 2012; as such emission decreased by approximately 1.9%, which increased again in 2013. The average amount of total GHG emission in this five years period was 1.78 × 106 tons of carbon dioxide equivalent/year (t CO2 eq. y−1). Active fishing gear was found to consume 20% more fuel than passive gear. However, the production from passive gear was 28%, lower than 72% from active gear. The reason for this is that less abundant stationary resources are harvested using passive gear. Furthermore, the consumption of fuel was significantly influenced by the fishing method. Implementation and development of new fishing technologies and methods are important for improving energy efficiency and reducing the climate impact on fisheries. To realize these purposes, the fishery management system needs to be established by centralizing on energy efficiency and climate effect.

A survey of Scottish fishermen ahead of Brexit: political, social and constitutional attitudes

There is a substantial amount of literature that focuses on the governance of offshore fisheries in Europe and abroad, the history of fishing industries in different countries, and anthropological studies of fishing communities around the world. There is also a large amount of literature that explores the attitudes of fishermen towards fisheries governance and management. However, there is very little research that has explored the political attitudes of fishermen through the use of quantitative survey data. Using a survey carried out just ahead of the referendum on the UK’s membership of the EU, this paper analyses data from a sample of Scottish skippers who work on vessels over 10 m in length. The paper focuses on how fishermen in Scotland vote at both UK and Scottish elections, how they voted in the Scottish independence and EU referendums, their political and social attitudes and their demographic breakdown. On the EU referendum, the paper finds that fishermen, as well intending to overwhelmingly voting to leave the EU, did so for instrumental reasons in the belief that this course of action would benefit them and their industry.

Applications on the Yield Structure of Aquatic Products and the Structure of Fishery Human Resources in Zhoushan Based on Factor Analysis

Based on factor analysis, this paper mainly analyzed the yield structure of aquatic products and the structure of fishery human resources in Zhoushan city during 2000-2013. Through a comprehensive analysis of the result of factor analysis, the research put forward some related suggestionsthat adjust the yield structure of aquatic products and the structure of fishery manpower resources, develop offshore fisheries and marine aquaculture industry, and build the marine ranching and artificial fish-reefs. On the basis of maintaining certain fishing intensity, it is necessary to adjust the manpower resources in the deep processing of aquatic products and trade aspect.

Applications on the Yield Structure of Aquatic Products and the Structure of Fishery Human Resources in Zhoushan Based on Factor Analysis

Based on factor analysis, this paper mainly analyzed the yield structure of aquatic products and the structure of fishery human resources in Zhoushan city during 2000-2013. Through a comprehensive analysis of the result of factor analysis, the research put forward some related suggestionsthat adjust the yield structure of aquatic products and the structure of fishery manpower resources, develop offshore fisheries and marine aquaculture industry, and build the marine ranching and artificial fish-reefs. On the basis of maintaining certain fishing intensity, it is necessary to adjust the manpower resources in the deep processing of aquatic products and trade aspect.

Transient movements of a deep‐water flatfish in coastal waters: Implications of inshore‐offshore connectivity for fisheries management

Abstract Globally, small‐scale inshore fisheries are being recognized as highly beneficial for underdeveloped coastal communities since they directly contribute to local economies. Community coastal fisheries, however, may target species that are simultaneously harvested by large commercial vessels in adjacent offshore waters, creating uncertainty over stock units and connectivity that complicate management. Greenland halibut Reinhardtius hippoglossoides, a commercially important flatfish species in the Arctic, were tagged in Scott Inlet, coastal Baffin Island, Canada, with acoustic transmitters and tracked for a 1‐year period. Our aim was to measure fish movement and connectivity between inshore habitats, where Inuit fisheries are developing, and offshore waters, where an established commercial fishery operates. Four movement metrics were established, and cluster analysis and a mixed effects model were used to define movement types and identify environmental covariates of the presence/absence within the coastal environment respectively. Two distinct movement patterns were characterized for Greenland halibut; the majority were transients that were no longer detected inshore by the end of November (n = 47, 72%), and a smaller group of intermittently resident fish that moved into the offshore at the same time as transient fish, but returned to the coastal environment in the winter (n = 8, 12%), with the remainder being undefined. The presence of Greenland halibut in the inshore was negatively correlated with ice cover, indicating that fish moved offshore as sea ice formed. Synthesis and applications. Greenland halibut were previously thought to be highly resident within the coastal environment of Baffin Bay; however, our data demonstrates that this is not true for all areas. In Scott Inlet and adjacent coastal regions, Greenland halibut exhibit complex inshore‐offshore connectivity, suggesting inshore and offshore fisheries require a shared quota. We recommend that in the face of developing global small‐scale coastal fisheries, improved understanding of stock connectivity between environments is required to sustainably manage commercial fish species.

Evaluation of the potential genotoxic activity in seawater of Asin Bay, Gulf of Gulluk, Mugla, Aegean coast of Turkey

This research examined the genotoxic activity in the seawater of Asin Bay (Gulf of Gulluk) located in Mugla, Turkey, Aegean coast of Turkey. Genotoxic activities of 66 raw samples, taken from 17 different stations in the spring and summer seasons of the year 2013, were determined by using in vitro mutagenicity assay SOS chromotest with Escherichia coli PQ37 strain bacteria activities. In the applied procedure, β-galactosidase (β-gal) activity, alkaline phosphatase (AP) activity, and different solvent controls were taken into account to generate reliable results in terms of the corrected induction factors (CIF) used as a quantitative measure of genotoxic activity level. The SOS chromotest procedure was simply and rapidly performed as an early assay to explore for whether a potential genotoxic activity was presence in the in the seawater of Asin Bay (Gulf of Gulluk) with no special measuring devices except a microplate reader. The implemented assay was successfully completed within only 24 h including the revival of the bacteria. The results showed that 11 samples (%17 of total) were close to the threshold value of 1.5. The findings of this study clearly revealed that the seawater of Asin Bay (Gulf of Gulluk) had no potential genotoxic risks in terms of the organisms in marine ecosystem, since all of the calculated CIF values were determined to be below the threshold level. It was concluded that according to the SOS chromotest results, the levels of potential genotoxic agents were found to be under the limits for the offshore fishery.

AHP를 이용한 요인별ㆍ그룹별 어선감척 목표량 비교 분석

The aims of this study are to estimate and assign the weight of each evaluation factor using the AHP technique which considers not only the technical·socio-economic factors, but also the resource status of the fish stock in order to derive the optimal vessel reduction scales. In order to set the optimal level in Korea, a questionnaire survey was conducted by public officials, professors, researchers, and industry workers. According to the results of the questionnaire, the weight of evaluation factor to be set in the vessel reduction was given. In addition, we compared and analyzed the effect of weight difference of important factors by group. As a result, public officials, professors, and researchers took a high weight of biological factors, otherwise industry workers took a high weight of socio-economic factors. Also, the optimal vessel reduction scales reflecting only the fishing effort level based on the resource assessment were 3,874 vessels in coastal fishery, and 222 vessels in offshore fishery. On the other hand, the optimal vessel reduction scales considering the technical factors and socio-economic factors were 3,513 vessels in coastal fishery, and 203 vessels in offshore fishery. In the analysis by group, the optimal vessel reduction scales of industry workers were relatively lower than those of public officials, researchers and professors.

Characterizing Coastal Ecosystem Service Trade-offs with Future Urban Development in a Tropical City.

With rapid urbanization in the coastal zone and increasing habitat losses, it is imperative to understand how urban development affects coastal biodiversity and ecosystem service provision. Furthermore, it is important to understand how habitat fragments can best be incorporated into broader land use planning and coastal management, in order to maximize the environmental benefits they provide. In this study, we characterized the trade-offs between (a) urban development and individual mangrove environmental indicators (habitat quality and ecosystem services), and (b) between different environmental indicators in the tropical nation of Singapore. A range of biological, biophysical, and cultural indicators, including carbon, charcoal production, support for offshore fisheries, recreation, and habitat quality for a threatened species were quantified using field-based, remote sensing, and expert survey methods. The shape of the trade-off Pareto frontiers was analyzed to assess the sensitivity of environmental indicators for development. When traded off individually with urban development, four out of five environmental indicators were insensitive to development, meaning that relatively minor degradation of the indicator occurred while development was below a certain threshold, although indicator loss accelerated once this threshold was reached. Most of the pairwise relationships between the five environmental indicators were synergistic; only carbon storage and charcoal production, and charcoal production and recreational accessibility showed trade-offs. Trade-off analysis and land use optimization using Pareto frontiers could be a useful decision-support tool for understanding how changes in land use and coastal management will impact the ability of ecosystems to provide environmental benefits.

Filling the gap: Using fishers’ knowledge to map the extent and intensity of fishing activity

Knowledge of the extent and intensity of fishing activities is critical to inform management in relation to fishing impacts on marine conservation features. Such information can also provide insight into the potential socio-economic impacts of closures (or other restrictions) of fishing grounds that could occur through the future designation of Marine Conservation Zones (MCZs). We assessed the accuracy and validity of fishing effort data (spatial extent and relative effort) obtained from Fishers’ Local Knowledge (LK) data compared to that derived from Vessel Monitoring System (VMS) data for a high-value shellfish fishery, the king scallop (Pecten maximus L.) dredge fishery in the English Channel. The spatial distribution of fishing effort from LK significantly correlated with VMS data and the correlation increased with increasing grid cell resolution. Using a larger grid cell size for data aggregation increases the estimation of the total area of seabed impacted by the fishery. In the absence of historical VMS data for vessels ≤15 m LOA (Length Overall), LK data for the inshore fleet provided important insights into the relative effort of the inshore (<6 NM from land) king scallop fishing fleet in the English Channel. The LK data provided a good representation of the spatial extent of inshore fishing activity, whereas representation of the offshore fishery was more precautionary in terms of defining total impact. Significantly, the data highlighted frequently fished areas of particular importance to the inshore fleet. In the absence of independent sources of geospatial information, the use of LK can inform the development of marine planning in relation to both sustainable fishing and conservation objectives, and has application in both developed and developing countries where VMS technology is not utilised in fisheries management.

초월대수비용함수를 이용한 근해어업의 규모의 경제성 분석

This study estimates the cost function through offshore fishery cost data and analyzed the economies of scale of Korea's offshore fishery. For the estimation of the cost function, translog cost function was used, and the analysis implemented the panel analysis of the panel data. Also, annual economies of scale of the offshore fishery and economies of scale of 14 offshore fisheries in 2015 were analyzed using translog cost function coefficient estimation. The analysis result of economies of scale of Korea's offshore fishery showed that with the exception of 2003, economies of scale exist in all periods of time. However, as it almost reaches the minimum efficient scale, it was revealed that further scale expansion will bring inefficiency. Thus, according to the analysis result, Korea's offshore fishery requires a scale reduction policy rather than scale expansion policy, and this seems to coincide with the current government's fishery reconstruction policy and its practice such as the fishing vessel buyback program. The analysis result of economies of scale of each offshore fishery in 2015 showed that economies of scale of each offshore fishery exists with the exception of five trawl fisheries such as large pair-trawl and large otter trawl and large purse seines. This strongly suggests that the five fisheries and Large Purse Seines with non performing economies of scale need urgent scale reduction and should be the first target for the government's fishery reconstruction policy.

Lagoon nurseries make a major contribution to adult populations of a highly prized coastal fish

AbstractThis study investigated the contributions of five putative nursery areas, namely four coastal lagoons and the marine coastal zone, to the local offshore fishery of the gilthead sea bream Sparus aurata, in the Gulf of Lion (NW Mediterranean). A detailed database of multi‐elemental lagoon and marine otolith signatures was developed, based upon analysis of multiple sequential spots across growth bands of the otoliths of juveniles (n = 142) sampled from the habitats over a 5‐yr interval. Adults of 10 annual cohorts (n = 114), fished throughout the Gulf, were then submitted to a similar microchemical analysis of the growth band of their otoliths that was formed after nursery settlement in their first year. Using the juvenile signature database and Random Forest classification algorithms, adults were re‐assigned to the lagoons or marine coastal zone as a nursery. More than 80% of adults derived from lagoons, being ≥ 85.0% for five consecutive cohorts. Therefore, the marine coastal zone apparently contributed few adults, especially as a function of surface area. The four lagoons differed, however, in their contribution to the S. aurata fishery. Two lagoons qualified as “Effective Juvenile Habitats” that contributed more than 20% of the adults fished. Two shallow brackish lagoons were “Nursery‐Role Habitats” that contributed almost twice as many adults, per unit surface area, as the overall average. Such information can support strategies for sustainable management of multiple coastal lagoon habitats, and of valuable fisheries that depend upon them.

GLM-Based Analysis on Seasonal Variation of Fishery Resources in Dapeng Bay, China

Dapeng Bay is a typical offshore fisheries area in the South China Sea (SCS). In order to understand the fishery resources, seasonal variations of species composition, dominant species composition, standardized catch per unit effort (SCPUE) and community diversity of fishery resources in Dapeng Bay, China were analyzed based on trawl survey data in spring (March) and summer (May) of 2013 as well as autumn (August) and winter (December) of 2012. Results demonstrated that there are 113 fishery species, which belong to 78 categories, 50 families, 14 catalogues, 3 classes. There are the most species in summer (61 species) and about 56 species in other seasons. In all four seasons, fish and crustacea are dominant species, and there are the fewest cephalopoda. High values of SCPUE occur in spring and autumn, reaching 5.65 and 5.33, respectively. SCPUE is generally low in summer, ranging between 0.52 - 0.96. Fish biodiversity is the highest in summer and the lowest in winter. Among biodiversity, Shannon-Wiener diversity index, Margalef diversity index and Pielou evenness index vary in the same trend. They are decreasing from summer, spring, autumn to winter successively. Therefore, there are violent seasonal variation of species composition, quantity and structure of fishery resources in Dapeng Bay. The community structure and function are highly stable in summer, but they have poor stability in autumn and winter. This research can provide scientific references for protection and sustainable use of fishery resources in typical offshore fisheries area in the SCS.

Effect of decreased fishing effort off Fukushima on abundance of Japanese flounder (Paralichthys olivaceus) using an age‐structured population model incorporating seasonal coastal‐offshore migrations

AbstractOff Fukushima, Japanese flounder (Paralichthys olivaceus) is a highly‐valued species supporting coastal and offshore fisheries. We developed an age‐structured population model incorporating seasonal coastal‐offshore migrations to estimate and predict the abundance of Japanese flounder off Fukushima, where fishing has been restricted since the 2011 Fukushima Dai‐ichi Nuclear Power Plant (FNPP) accident. We estimated the abundance of Japanese flounder using catch per unit effort from coastal gill net and offshore bottom trawl fishing from January 2000 to February 2011 and predicted the abundance under two different fishing effort scenarios (the same effort level as 2010 or decreased effort after the FNPP accident). Estimated abundance reflected the seasonal coastal‐offshore migrations well, and it was estimated that abundance increased during and after 2007 because of high recruitments. In contrast, it was concluded that the predicted abundance on and after 2012 increased owing to the decreased fishing effort because the same estimated recruits were used in both scenarios. This indicates that the waters off Fukushima have effectively been serving as a marine protected area for Japanese flounder since the FNPP accident. This result was validated because almost all (83%) of the observed abundance index values calculated from a scientific bottom trawl survey during 2003–2014 were included within the estimated (predicted) 95% credible intervals of estimated (predicted) abundance index in the period. We also demonstrated the model's applicability for estimating the optimal fishing effort and age at first landing to maximize the earnings from gillnet and bottom trawl fisheries.