Decline of a blue swimmer crab (Portunus pelagicus) fishery in Western Australia—History, contributing factors and future management strategy

The spider crab Maja brachydactyla is an important commercial species in Europe and supports intensive fisheries in the NE Atlantic. A field survey was performed to assess long-term and consecutive interannual (2005)(2006)(2007)(2008)(2009)(2010) variation of the biochemical composition of newly hatched larvae of M. brachydactyla. Larval biochemical profiles differed significantly among years, with pronounced differences being recorded in 2010. Differences among batches of newly hatched larvae were mainly explained by the contribution of triacylglycerols and, to a lesser degree, by protein and lipid content. The use of different nutrition indices is discussed. The biochemical composition of newly hatched larvae from M. brachydactyla was highly variable, even though surveyed broodstock was obtained from the same local population and was always sampled during the same season. The unpredictable biochemical profiles of newly hatched larvae may condition their survival and recruitment. This largely overlooked aspect of larval variability should be considered in future fisheries management strategies and captive production of marine organisms that still rely on wild seeds.

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“…; Johnston et al . ). The growth and survival of crustacean larvae directly affect their recruitment and population size.…”

Section: Discussionmentioning

confidence: 97%

Interannual variability in the biochemical composition of newly hatched larvae of the spider crab Maja brachydactyla (Decapoda, Majidae)

et al. 2013

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“…However, methods of obtaining swimming crabs are directly dependent on natural stocks which, in turn, are vulnerable to pressure from overfishing, pollution or climate changes. Different combinations of these factors have been responsible for the decline of populations in recent years in many regions of the globe (Lindner 2005;Paolisso 2007;Shelley 2008;Zohar et al 2008;Johnston et al 2011;Shelley & Lovatelli 2011;Ikhwanuddin et al 2012).…”

Section: Obtaining Individualsmentioning

confidence: 99%

Systems and techniques used in the culture of soft‐shell swimming crabs

Silva¹,

Pereira

Ostrensky³

2017

Reviews in Aquaculture

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The academic interest in the production of soft‐shell swimming crabs has increased in direct proportion to the increasing demand worldwide for this gastronomic delicacy. The techniques of obtaining this product are essentially based on the maintenance of swimming crabs at premoult stage in open, semi‐closed or closed farming systems, until the moment of moulting. These different types of systems reflect the biological e environmental control method evolution. To achieve industrial scale production of soft swimming crabs, the option of using closed systems has increased in recent years. This type of system offers several advantages, such as greater control over environmental variables, greater ease of installation, higher storage densities, greater ease of monitoring ecdysis occurrence and, especially, the possibility of incorporating several forms of automation. In this review, the main production systems currently used, as well as the main techniques for obtaining the animals, their management under controlled conditions, harvesting and slaughter, are presented and discussed, focusing on future perspectives for the world production of soft‐shell swimming crabs.

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“…Additional initial analyses included the fitting of an unconstrained (in means and variances) mixture of two and three normal distributions to the length‐frequency data for all available months in years 1985 and 1986 (see Web Appendix C). The BSC is known to be a short lived species, reaching its maximal length within 2–3 years (Potter et al, ; Johnston et al, ). We concluded that it was likely that the BSC length‐frequency data were best modeled with a mixture of three normal distributions (Web Appendix C outlines further evidence for this choice).…”

Section: Application To Bscmentioning

confidence: 99%

Mixture of Time-Dependent Growth Models with an Application to Blue Swimmer Crab Length-Frequency Data

et al. 2016

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Understanding how aquatic species grow is fundamental in fisheries because stock assessment often relies on growth dependent statistical models. Length-frequency-based methods become important when more applicable data for growth model estimation are either not available or very expensive. In this article, we develop a new framework for growth estimation from length-frequency data using a generalized von Bertalanffy growth model (VBGM) framework that allows for time-dependent covariates to be incorporated. A finite mixture of normal distributions is used to model the length-frequency cohorts of each month with the means constrained to follow a VBGM. The variances of the finite mixture components are constrained to be a function of mean length, reducing the number of parameters and allowing for an estimate of the variance at any length. To optimize the likelihood, we use a minorization-maximization (MM) algorithm with a Nelder-Mead sub-step. This work was motivated by the decline in catches of the blue swimmer crab (BSC) (Portunus armatus) off the east coast of Queensland, Australia. We test the method with a simulation study and then apply it to the BSC fishery data.

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Decline of a blue swimmer crab (Portunus pelagicus) fishery in Western Australia—History, contributing factors and future management strategy

Cited by 57 publications

References 15 publications

Interannual variability in the biochemical composition of newly hatched larvae of the spider crab Maja brachydactyla (Decapoda, Majidae)

Interannual variability in the biochemical composition of newly hatched larvae of the spider crab Maja brachydactyla (Decapoda, Majidae)

Systems and techniques used in the culture of soft‐shell swimming crabs

Mixture of Time-Dependent Growth Models with an Application to Blue Swimmer Crab Length-Frequency Data

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