Estimates of growth and comparisons of growth rates determined from length- and age-based models for populations of purple wrasse (Notolabrus fucicola)

Growth of a temperate reefa-ssociated fish, the purple wrasse (Notolabrus fucicola), was examined from two sites on the east coast of Tasmania by using age- and length-based models. Models based on the von Bertalanffy growth function, in the standard and a reparameterized form, were constructed by using otolith-derived age estimates. Growth trajectories from tag-recaptures were used to construct length-based growth models derived from the GROTAG model, in turn a reparameterization of the Fabens model. Likelihood ratio tests (LRTs) determined the optimal parameterization of the GROTAG model, including estimators of individual growth variability, seasonal growth, measurement error, and outliers for each data set. Growth models and parameter estimates were compared by bootstrap confidence intervals, LRTs, and randomization tests and plots of bootstrap parameter estimates. The relative merit of these methods for comparing models and parameters was evaluated; LRTs combined with bootstrapping and randomization tests provided the most insight into the relationships between parameter estimates. Significant differences in growth of purple wrasse were found between sites in both length- and age-based models. A significant difference in the peak growth season was found between sites, and a large difference in growth rate between sexes was found at one site with the use of length-based models

Proposed allocation of research catches in Divisions 58.4.1 and

At WG-SAM-15, it was noted that 5 members, Australia, France, Japan, Korea and Spain had notified to conduct research in the exploratory toothfish fisheries off East Antarctica, covered by CCAMLR Divisions 58.4.1 and 58.4.2. This proposal seeks to establish an arrangement whereby all notified members have a catch allocation to undertake research, thereby avoiding Olympic fishing

Commercial fishing patterns influence odontocete whale-longline interactions in the Southern Ocean

The emergence of longline fishing around the world has been concomitant with an increase in depredation-interactions by odontocete whales (removal of fish caught on hooks), resulting in substantial socio-economic and ecological impacts. The extent, trends and underlying mechanisms driving these interactions remain poorly known. Using long-term (2003–2017) datasets from seven major Patagonian toothfish (Dissostichus eleginoides) longline fisheries, this study assessed the levels and inter-annual trends of sperm whale (Physeter macrocephalus) and/or killer whale (Orcinus orca) interactions as proportions of fishing time (days) and fishing area (spatial cells). The role of fishing patterns in explaining between-fisheries variations of probabilities of odontocete interactions was investigated. While interaction levels remained globally stable since the early 2000s, they varied greatly between fisheries from 0 to >50% of the fishing days and area. Interaction probabilities were influenced by the seasonal concentration of fishing effort, size of fishing areas, density of vessels, their mobility and the depth at which they operated. The results suggest that between-fisheries variations of interaction probabilities are largely explained by the extent to which vessels provide whales with opportunities for interactions. Determining the natural distribution of whales will, therefore, allow fishers to implement better strategies of spatio-temporal avoidance of depredation

Genetic structure of Patagonian toothfish populations from otolith DNA

© Antarctic Science Ltd 2016. The Patagonian toothfish, Dissostichus eleginoides, is a valuable fishery species and has a discontinuous distribution across the Southern Ocean. Identification of the genetic stock structure of toothfish would allow evaluation of the suitability of the spatial scale at which fisheries management operates. Genetic subdivision seems likely given the species distribution. Population genetics studies of this species have been performed; however, they have been limited by sample size, spatial coverage and/or the type of markers investigated. As a potential solution, we developed methods for extracting toothfish DNA from otoliths that are available in large numbers from collections held at several research institutes. Genetic differentiation between the three oceanic sectors was investigated. Four mitochondrial and four nuclear markers with multiple single nucleotide polymorphisms were sequenced by high throughput sequencing for samples from six locations. Genetic differentiation was found between three sectors with nuclear markers. However, only the Pacific sector was differentiated from other sectors with mitochondrial markers. This study demonstrates the usefulness of otolith DNA as a means of increasing sample sizes for population genetics research of fish. Additionally, the combination of nuclear and mitochondrial markers may allow insight into how the observed differences in movements between male and female toothfish impact population structure

Southern elephant seals (<i>Mirounga leonina</i> Linn.) depredate toothfish longlines in the midnight zone

<div><p>Humans have devised fishing technologies that compete with marine predators for fish resources world-wide. One such fishery for the Patagonian toothfish (<i>Dissostichus eleginoides</i>) has developed interactions with a range of predators, some of which are marine mammals capable of diving to extreme depths for extended periods. A deep-sea camera system deployed within a toothfish fishery operating in the Southern Ocean acquired the first-ever video footage of an extreme-diver, the southern elephant seal (<i>Mirounga leonina</i>), depredating catch from longlines set at depths in excess of 1000m. The interactions recorded were non-lethal, however independent fisheries observer reports confirm elephant seal-longline interactions can be lethal. The seals behaviour of depredating catch at depth during the line soak-period differs to other surface-breathing species and thus presents a unique challenge to mitigate their by-catch. Deployments of deep-sea cameras on exploratory fishing gear prior to licencing and permit approvals would gather valuable information regarding the nature of interactions between deep diving/dwelling marine species and longline fisheries operating at bathypelagic depths. Furthermore, the positive identification by sex and age class of species interacting with commercial fisheries would assist in formulating management plans and mitigation strategies founded on species-specific life-history strategies.</p></div

Comparison of independently derived benthic invertebrate and demersal fish ecoregionalisations for the Kerguelen Plateau

International audienceEcoregionalisation is a process that aims to identifyareas with distinct biological content and associatedenvironmental conditions. It improves on manytraditional approaches to regionalisation by explicitlyincorporating biological data into classifications.Ecoregionalisations are useful for improving our ecologicalunderstanding of marine ecosystems and forinforming spatial management. This includes providinginformation to aid in defining and prioritising areas forconservation, evaluating current spatial managementarrangements, targeting monitoring efforts and managinghuman activities (e.g. Grant et al., 2006; Douglass etal., 2014). The Kerguelen Plateau is a highly productiveregion of the southern Indian Ocean that supports lucrativedemersal fisheries (Duhamel and Welsford, 2011).It is subject to spatial management in the form of marineprotected areas (MPAs) with varying levels of protection(Commonwealth of Australia, 2014; Koubbi et al.,2016). Recently two ecoregionalisations have been independentlygenerated for the northern Kerguelen Plateau;one for benthic invertebrates (Martin et al., 2018) andanother for demersal fish (Hill et al., 2017). Here weconduct a preliminary analysis examining the congruencebetween these ecoregionalisations that representdifferent components of the demersal ecosystem

Total Allowable Catches (TAC’s) for Patagonian toothfish (<i>Dissostichus eleginoides</i>) and population estimates for the southern elephant seal (<i>Mirounga leonina</i>).

<p>Southern Hemisphere polar projection showing the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) boundaries, national Exclusive Economic Zones (EEZ’s), TAC’s for Patagonian toothfish within CCAMLR regions (red bubbles), southern elephant seal population estimates (black bubbles) and ocean bathymetry (blue shading; light = shallow). Figure produced by the Australian Antarctic Data Centre (c) Commonwealth of Australia 2016. Bathymetry: GEBCO (General Bathymetric Chart of the Oceans) 2014 grid, version 20150318. Coastline: Antarctic Digital Database version 6 (Antarctica), DeLorme, ESRI (other coastlines).</p