Application of a mixed modelling approach to standardize catch-per-unit-effort data for an abalone dive fishery in Western Victoria, Australia

Despite the prevalence of catch per unit effort (CPUE) as a key metric in fisheries assessments it can be fraught with inherent problems that often cause its use as an index of abundance to become contentious. This is particularly the case with abalone, a sedentary shellfish targeted by commercial dive fishers around the globe. It is common practice to standardize CPUE to at least partly address issues about how well it reflects the actual abundance of a stock. Differences between standardized and unstandardized trends may lead to controversy between scientists and stakeholders when standardized trends provide a less optimistic picture of stock status. It is within this context that we applied Linear Mixed Model (LMM) and Generalized Linear Mixed Model (GLMM) methods to standardize CPUE for the Western Zone blacklip abalone fishery in Victoria, Australia. This fishery was chosen for our evaluation because it included substantial population losses from a disease shock during the middle of the time series. The effects of diver, reef location, month and their interactions with year were included as random effects in these models and the results compared with nominal geometric means. The two standardization methods provided similar standardized CPUE trends and clearly demonstrated that a large proportion of the variance could be attributed to diver and spatial effects. The GLMM seemed to explain more variability in the data and produced better precision for standardized CPUEs than LMM. The temporal trend in variability attributed to divers and spatial scales reveals the impact of disease as well as any homo/heterogeneity effect. The CPUE trends responded to the impact of disease against a backdrop of declining stock, however when compared with the inter-annual pattern in nominal CPUE, the standardized trends showed that the decline immediately following the onset of disease was less precipitous. In contrast to what appeared to be an increase in the nominal series during the more recent post-disease period, there was only a slight non-significant increase observable in the standardized trends

The novel use of harvest policies and rapid visual assessment to manage spatially complex abalone resources (Genus Haliotis)

The novel use of harvest policies and rapid visual assessment to manage spatially complex abalone resources (Genus Haliotis

A multidimensional analysis of marine capture fisheries in China’s coastal provinces

AbstractChina (herein referred as China’s mainland, and excluding Hong Kong, Macau and Taiwan) is the largest contributor to global seafood production. While China’s marine fisheries have been extensively documented, there is a gap in systematically quantifying production of its marine fisheries and the different challenges confronting them at the provincial level. We addressed this gap in spatial detail by providing a review that compares and contrasts the exploitation history of China’s fisheries at both the national and provincial levels based on official statistical data. We expanded upon this to explore aspects of bio-socio-economic challenges faced by the country’s 11 fishing provinces. Our analysis suggested that significant increases in domestic marine catches in China have been accompanied by escalating fishing power, which has had differential impacts at the provincial scale. Catch per unit effort (CPUE) sharply declined at both the national and provincial scales, and many traditionally targeted demersal fish stocks showed clear downward trends in terms of catches. The 11 fishing provinces in China can be grouped into four clusters with distinct biological, social, and economic attributes. Targeted measures are recommended accordingly when implementing fisheries management measures for each specific fishing province in order to deliver an overall improvement in the sustainability of China’s marine fisheries

Overcoming gaps in a seasonal time series of Japanese anchovy abundance to analyse interannual trends

Overcoming gaps in a seasonal time series of Japanese anchovy abundance to analyse interannual trend

Mortality of silver eels migrating through different types of hydropower turbines in Lithuania

AbstractHydropower plants (HPP) are considered to be one of the major threats to the survival of European eels when they migrate downstream along inland water bodies during the early part of their annual journey to the spawning area in the Sargasso Sea. There are 98 HPPs in Lithuania and thousands throughout Europe. Numerous studies describe HPP induced mortality rates among European eels as variable depending on local, environmental, and technical factors. This heterogeneity in effect complicates theoretical extrapolation to eel mortality arising from specific types of HPP, necessary for effective management of local stocks. Silver eel mortality was estimated for 4 different HPPs in Lithuania. Mortality was estimated using RFID (Radio Frequency Identification, passive integrated transponders) tags and acoustic telemetry in a large HPP (>100 MW) with Kaplan turbines, a small HPP (<1 MW) with a Kaplan turbine and a fish passage, and for the first time in two small HPPs (<1 MW) with CINK turbines. The results supported a hypothesis that the mortality rate of migrating eels depends mainly on the type and size of the turbine. HPP induced mortality varied from 100% in a small CINK turbine down to 25% in the large HPP with Kaplan turbines. The importance of simple mitigation measures was highlighted by 34% of all tagged eels bypassing one of the HPP via an adjacent fish passage constructed for upstream migration of salmonids. The observed differences in mortality provide essential information for long term strategies designed to restore depleted eel populations in Lithuania and other European countries

Silver eel, Anguilla anguilla (Linnaeus, 1758), migration patterns in lowland rivers and lagoons in the North-Eastern region of their distribution range

Silver eel, Anguilla anguilla (Linnaeus, 1758), migration patterns in lowland rivers and lagoons in the North-Eastern region of their distribution rang

Contrasting stock status trends obtained from survey and fishery CPUE, taking Larimichthys polyactis in Yellow Sea Large Marine Ecosystem as an example

Contrasting stock status trends obtained from survey and fishery CPUE, taking Larimichthys polyactis in Yellow Sea Large Marine Ecosystem as an exampl

Research on utilization conflicts of fishery resources and catch allocation methods in the Bohai Sea, China

Research on utilization conflicts of fishery resources and catch allocation methods in the Bohai Sea, Chin

The feasibility of estimating biological parameters using electronic length frequency analysis (ELEFAN): The Bohai Sea as a case study

The feasibility of estimating biological parameters using electronic length frequency analysis (ELEFAN): The Bohai Sea as a case stud

Achieving greater equity in allocation of catch shares: A case study in China

The allocation of catch shares among fishing entities is a key element of a total allowable catch control system. Current allocation schemes fall short in their ability in terms of ensuring fairness and feasibility and there is much scope for improvement. In this study, a new allocation method based on applying a relative deprivation coefficient is introduced into the allocation of catch shares, and demonstrated in a case study involving the 11 coastal provinces in China. Advantages of this process of quota allocation in comparison with well-established allocation methods were investigated. Compared with the conventional single-criterion approach and simple multi-criteria-based allocation with equal weights, the new allocation scheme integrating the new weighting method with multi-criteria allocation showed superior performance in rendering the outcomes in catch shares allocation fairer and more reasonable, with a Gini coefficient below 0.2. Quota proportions for the 11 coastal provinces under the newly developed allocation scheme were between maximum and minimum ratios of those under schemes using a single-criterion, which shows strong utility in reducing the rigidity of a single-criterion allocation approach and improving the acceptability of the allocation results. This study offers a viable yet fairer alternative for facilitating sustainable fisheries via quota management and provides a reference for fisheries policy makers in equitably allocating catch shares