An Examination of Sustainable Management of Pacific Bluefin Tuna Stock

Global distribution of platyhelminth parasites and their host specificities are not well known. Our hypothesis was that platyhelminth parasites of large pelagic fishes are common around the world. We analysed molecular variation in three different taxa of platyhelminth parasites infecting four species of tunas: yellowfin tuna (Thunnus albacares, Scombridae) from Western Australia, southern bluefin tuna (Thunnus maccoyii, Scombridae) from South Australia, Pacific bluefin tuna (Thunnus orientalis, Scombridae) from Pacific Mexico and northern bluefin tuna (T. thynnus, Scombridae) from two localities in the Mediterranean (Spain and Croatia). Comparisons of ITS2 and partial 28S rDNA demonstrated two congeneric species of blood flukes (Digenea: Sanguinicolidae) from multiple hosts and localities: Cardicola forsteri from southern bluefin and northern bluefin tunas, and Cardicola sp. from Pacific bluefin and northern bluefin tunas; and a gill fluke, Hexostoma thynni (Polyopisthocotylea: Hexostomatidae), from yellowfin, southern bluefin and northern bluefin tunas. Partial 28S rDNA indicates that a second type of fluke on the gills, Capsala sp. (Monopisthocotylea: Capsalidae), occurs on both southern bluefin and Pacific bluefin tunas. This appears to be the first report of conspecific platyhelminth parasites of teleosts with a wide‐ranging geographical distribution that has been confirmed through molecular approaches. Given the brevity of the free‐living larval stage of both taxa of flukes on the gills (H. thynni and Capsala sp.), we conclude that the only feasible hypothesis for the cosmopolitan distribution of these flatworms is migrations of host tunas. Host migration also seems likely to be responsible for the widespread occurrence of the two species of blood flukes (Cardicola spp.), although it is also possible that these were translocated recently by the spread of infected intermediate hosts.

This paper is to present a framework to analyse international relations regarding protection and exploitation of an endangered species. The question of how to balance conservation and consumption in order to maintain the sustainability of resources and nature is not only the central challenge of conservation ecology, but also an international political and economic issue that frequently leads to confrontation between countries. In relation to whales, for example, Japan has long been subjected to criticism by anti-whaling countries such as the United States and Australia, and has faced off against them on the international stage. And, more recently, similar confrontations have begun to appear in relation to tuna and eel. It has been highlighted in recent years that Pacific Bluefin Tuna are becoming endangered, and there is considerable national and international concern with regard to their resource management. This paper first obtains an implication about the course of events that led to the fishing ban. The implication is applied to the case of Pacific Bluefin Tuna. Pacific Bluefin Tuna and the whaling issue reveals points of commonality. The conclusion is that history of the whaling issue implies that Japan will lose the support not only of countries opposed to fishing but also of neutral countries, if Tokyo continues to adopt policies which make light of resource conservation. Even a total ban on the fishing of Pacific Bluefin Tuna may result. This implication from the whaling issue is potentially helpful to predict the development of international relations and conservation regarding other endangered species.

We examined the effects of feeding conditions and size differences on the aggressive behaviour and cannibalism in Pacific bluefin tuna (PBT) Thunnus orientalis larvae. In a 24 h experiment, restricted feeding alone was found to remarkably increase the frequency of aggressive behaviour, which was further elevated by differences in fish size. In a 4-day rearing experiment, while aggressive behaviour was increased by restricted feeding alone, the frequency of cannibalism did not change significantly. Although the frequency of aggressive behaviour did not increase with difference in size factor, small fish in this group gradually tended to die over 4-day period. In the restricted feeding and size difference group, large fish were observed to bite the small fish, and almost all the small fish died on the day after the start of the experiment. These results suggest that the aggressive behaviour of PBT larvae is chiefly increased by the shortage of live food; however, deaths related to cannibalism mainly occurred in small larvae and rapidly increased with food restriction and differences in fish size.

Pacific bluefin tuna (Thunnus orientalis) is a highly migratory, commercially valuable species potentially vulnerable to acoustic noise generated from human activities which could impact behavior and fitness. Although significant efforts have been made to understand hearing abilities of fishes, the large size and need to continuously swim for respiration have hindered investigations with tuna and other large pelagic species. In this study, Pacific bluefin tuna were trained to respond to a pure tone sound stimulus ranging 325-800 Hz and their hearing abilities quantified using a staircase psychophysical technique. Hearing was most sensitive from 400 to 500 Hz in terms of particle motion (radial acceleration -88 dB re 1 m s(-2); vertical acceleration -86 dB re 1 m s(-2)) and sound pressure (83 dB re 1 μPa). Compared to yellowfin tuna (Thunnus albacares) and kawakawa (Euthynnus affinis), Pacific bluefin tuna has a similar bandwidth of hearing and best frequency, but greater sensitivity overall. Careful calibration of the sound stimulus and experimental tank environment, as well as the adoption of behavioral methodology, demonstrates an experimental approach highly effective for the study of large fish species in the laboratory.

Fish represent a politically regulated, scientifically researched, industrially processed, commercially marketed and socially contested living marine resource. Related to this, the incorporation of resource users and stakeholders into fisheries management is particularly important. Such involvement has recently improved in terms of frequency, but institutional frameworks often result in a lack of recognition and integration of the diverse ‘knowledges’ of stakeholders involved. Against this background, we aim to uncover the potentials of additional knowledge types for management purposes, paving the way toward a more collaborative management. We first conducted qualitative expert interviews with different stakeholder groups (e.g., commercial fisheries, eNGO and administration) to map various ‘knowledges’ about cod (Gadus morhua), a major resource species in the Western Baltic Sea to reveal the various experiences and epistemologies revolving around it. The second analytical step consisted of examining how these ‘knowledges’ structure, inform and often enter into conflict with perspectives on and assessments of fisheries management. Potentials were identified regarding enhanced stakeholder engagement in management processes that provide food for thought to seek change in sustainable management of fish stocks in the future. Our study is a pointer to the need to transform fisheries management in a more social and participatory way. We argue that sustainable natural resource management cannot be designed solely by integrating more ‘knowledges’ (knowledge sharing) but requires the creation of social contexts and institutions with stakeholder empowerment at the local level (power sharing) to sustainably manage natural resources such as commercially importance fish stocks.

Pacific bluefin tuna (Thunnus orientalis; PBFT) is a highly migratory species, with some individuals migrating between the western Pacific Ocean (WPO) and eastern Pacific Ocean (EPO). In this study, we used stable isotope analysis to identify PBFT that had recently undergone westward transoceanic migration on the Sea of Japan. A total of 155 PBFT individuals were examined. Their ages ranged from 2 to 17 years, with most individuals being 2–7 years of age. Individuals from each year class were classified as WPO residents or recent EPO migrants using cluster analysis of δ15N values. Individuals aged 2, 6, and over 7 years had unimodal distributions of δ15N values, while individuals aged 3, 4 and 5 years showed a bimodal distribution with high- and low-δ15N groups. Due to the overall higher baseline of δ15N values in the EPO, high δ15N individuals were considered to represent PBFT that had migrated from the EPO. Though individuals aged 6 and over 7 years showed unimodal distributions in the cluster analysis, discriminant analysis indicated that these PBFT also included some migrants from the EPO. We preliminary estimated the percentages of migrants and residents in the Sea of Japan. Such information can improve stock assessments models for PBFT and contribute to the sustainable stock management of this species.

Stop the global slaughter of sharks

Elucidating fishing effects on fish population dynamics is a critical step toward sustainable fisheries management. Despite previous studies that have suggested age or size truncation in exploited fish populations, other aspects of fishing effects on population demography, e.g., via altering life histories and density, have received less attention. Here, we investigated the fishing effects altering adult demography via shifting reproductive trade-offs in the iconic, overexploited, Pacific bluefin tuna Thunnus orientalis. We found that, contrary to our expectation, mean lengths of catch increased over time in longline fisheries. On the other hand, mean catch lengths for purse seine fisheries did not show such increasing trends. We hypothesized that the size-dependent energetic cost of the spawning migration and elevated fishing mortality on the spawning grounds potentially drive size-dependent skipped spawning for adult tuna, mediating the observed changes in the catch lengths. Using eco-genetic individual-based modeling, we demonstrated that fishing-induced evolution of skipped spawning and size truncation interacted to shape the observed temporal changes in mean catch lengths for tuna. Skipped spawning of the small adults led to increased mean catch lengths for the longline fisheries, while truncation of small adults by the purse seines could offset such a pattern. Our results highlight the eco-evolutionary dynamics of fishing effects on population demography and caution against using demographic traits as a basis for fisheries management of the Pacific bluefin tuna as well as other migratory species.

Dynamic energy budget (DEB) theory offers a systematic, though abstract, way to describe how an organism acquires and uses energy and essential elements for physiological processes, in addition to how physiological performance is influenced by environmental variables such as food density and temperature. A 'standard' DEB model describes the performance (growth, development, reproduction, respiration, etc.) of all life stages of an animal (embryo to adult), and predicts both intraspecific and interspecific variation in physiological rates. This approach contrasts with a long tradition of more phenomenological and parameter-rich bioenergetic models that are used to make predictions from species-specific rate measurements. These less abstract models are widely used in fisheries studies; they are more readily interpretable than DEB models, but lack the generality of DEB models. We review the interconnections between the two approaches and present formulae relating the state variables and fluxes in the standard DEB model to measured bioenergetic rate processes. We illustrate this synthesis for two large fishes: Pacific bluefin tuna (Thunnus orientalis) and Pacific salmon (Oncorhynchus spp.). For each, we have a parameter-sparse, full-life-cycle DEB model that requires adding only a few species-specific features to the standard model. Both models allow powerful integration of knowledge derived from data restricted to certain life stages, processes and environments.

We investigate the impact of oceanographic variability on Pacific bluefin tuna (Thunnus orientalis: PBF) distributions in the California Current system using remotely sensed environmental data, and fishery‐dependent data from multiple fisheries in a habitat‐modeling framework. We examined the effects of local oceanic conditions (sea surface temperature, surface chlorophyll, sea surface height, eddy kinetic energy), as well as large‐scale oceanographic phenomena, such as El Niño, on PBF availability to commercial and recreational fishing fleets. Results from generalized additive models showed that warmer temperatures of around 17–21°C with low surface chlorophyll concentrations (<0.5 mg/m3) increased probability of occurrence of PBF in the Commercial Passenger Fishing Vessel and purse seine fisheries. These associations were particularly evident during a recent marine heatwave (the “Blob”). In contrast, PBF were most likely to be encountered on drift gillnet gear in somewhat cooler waters (13–18°C), with moderate chlorophyll concentrations (0.5–1.0 mg/m3). This discrepancy was likely a result of differing spatiotemporal distribution of fishing effort among fleets, as well as the different vertical depths fished by each gear, demonstrating the importance of understanding selectivity when building correlative habitat models. In the future, monitoring and understanding environmentally driven changes in the availability of PBF to commercial and recreational fisheries can contribute to the implementation of ecosystem approaches to fishery management.

Characterization of digestive physiology in Pacific bluefin tuna Thunnus orientalis juveniles fed a raw fish feed and a commercial diet

Against the backdrop of increasingly interconnected environmental, social, and governance (ESG) challenges, enterprises must formulate sustainable strategies to achieve synergistic development among economic performance, social responsibility, and ecological conservation. As a core organizational resource, human resources serves as a critical enabler for fulfilling corporate social responsibility (CSR) and driving sustainable development. Whether enterprises can enhance the contribution of human resources to the fulfillment of corporate social responsibility and sustainable development is an important issue that currently needs to be studied in the field of human resource management. Therefore, this research follows the grounded theory method, integrates CSR and sustainable development theories, and uses systematic thinking to deeply explore the concept and structure of sustainable human resource management systems, and it develops relevant scales and combines exploratory and confirmatory factor analysis methods to revise and validate the scales. The research results show that the sustainable human resource management system is a multidimensional concept, including the following: employee rights protection, employee training and development, employee occupational health, employee relations management, and sustainable development management; its measurement scale contains five factors, with a total of 20 items. The results of factor analysis indicate that the reliability and validity tests of the developed scale have reached an ideal level. The research results enrich the concept and connotation of sustainable human resource management systems, and the development of the sustainable human resource management systems scale aims to promote the extension of the field of sustainable human resource management systems from theoretical exploration to empirical analysis research, providing a theoretical basis for Chinese enterprises to achieve sustainable development goals.

Compound specific isotopic analysis (CSIA) of amino acids has received increasing attention in ecological studies in recent years due to its ability to evaluate trophic positions and elucidate baseline nutrient sources. However, the incorporation rates of individual amino acids into protein and specific trophic discrimination factors (TDFs) are largely unknown, limiting the application of CSIA to trophic studies. We determined nitrogen turnover rates of individual amino acids from a long-term (up to 1054 days) laboratory experiment using captive Pacific bluefin tuna, Thunnus orientalis (PBFT), a large endothermic pelagic fish fed a controlled diet. Small PBFT (white muscle δ15N∼11.5‰) were collected in San Diego, CA and transported to the Tuna Research and Conservation Center (TRCC) where they were fed a controlled diet with high δ15N values relative to PBFT white muscle (diet δ15N∼13.9‰). Half-lives of trophic and source amino acids ranged from 28.6 to 305.4 days and 67.5 to 136.2 days, respectively. The TDF for the weighted mean values of amino acids was 3.0 ‰, ranging from 2.2 to 15.8 ‰ for individual combinations of 6 trophic and 5 source amino acids. Changes in the δ15N values of amino acids across trophic levels are the underlying drivers of the trophic 15N enrichment. Nearly all amino acid δ15N values in this experiment changed exponentially and could be described by a single compartment model. Significant differences in the rate of 15N incorporation were found for source and trophic amino acids both within and between these groups. Varying half-lives of individual amino acids can be applied to migratory organisms as isotopic clocks, determining the length of time an individual has spent in a new environment. These results greatly enhance the ability to interpret compound specific isotope analyses in trophic studies.

Commercial fish species of inland waters: A model for sustainability assessment and management

Uvaria chamae P. Beauv is known as a key shrub species providing several goods and services for sustaining livelihoods in Sub-Saharan Africa. Despite its great medicinal importance for local communities, little is known about its conservation status and sustainable management strategies regarding the current overexploitation of the species’ fruits through traditional agroforestry systems. Here, we addressed a global systematic review of the current state of knowledge on several aspects of research of U. chamae for setting further breeding programmes and conservation initiatives. A total of 744 publications were identified based on the extensive bibliometric review of its sustainable management and conservation status over the last three decades (1991-2021) through existing online databases. Only 257 publications were finally included in the current review after deep scrutinization which were in line with several aspects of the conservation ecology and management of U. chamae in Africa. All retained papers came globally from the five sub-regions, and particularly 13 countries in Africa. Most of them were recorded in West Africa (n = 245) compared to the other sub-regions where few studies exist on this intensively harvested shrub species. Approximately 89% of the retained publications came from five of West African countries including Nigeria (n = 151), Benin (n = 30), Côte d'Ivoire (n = 18), Guinea (n = 16), and Togo (n = 14). In-depth bibliometric analysis revealed critical knowledge gaps on U. chamae in terms of its geographic distribution; conservation status; tree growth, productivity and propagation; morphological diversity; molecular genetic diversity; reproductive biology; ecophysiological performances; socio-economic importance; biochemical analysis; and structural characterization. The current review paves the way for developing further long-term management programs of U. chamae in Africa.