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Butts I.A.E.,Technical University of Denmark | Ben Khemis I.,Instm Institute National Des Science Et Technologies Of La Mer | Litvak M.K.,Mount Allison University
Aquaculture International | Year: 2015

In the period from 4 days post-hatching to metamorphosis, winter flounder that were naïve to artificial feed were exposed to an artificial diet and allowed to forage for 8 min. The presence or absence of artificial diet in the gut was used as an indicator of acceptance. The relationship between diet acceptance and age was found to be a dome-shaped function (incidence of ingested food = −0.0233 day2 + 1.101 day − 4.9428, r2 = 0.85). Here, our analysis suggests that winter flounder should be exposed to artificial diets by 26 days post-hatch at 10 °C, after this time receptivity declines. This age corresponds to larvae that are in the flexion developmental stage and have a standard length between 5.95 and 6.23 mm. © 2014, Springer International Publishing Switzerland.

Hattab T.,Inat Institute National Agronomique Of Tunisie | Hattab T.,IRD Montpellier | Ben Rais Lasram F.,Inat Institute National Agronomique Of Tunisie | Albouy C.,University of Quebec at Rimouski | And 5 more authors.
PLoS ONE | Year: 2013

Bottom trawl survey data are commonly used as a sampling technique to assess the spatial distribution of commercial species. However, this sampling technique does not always correctly detect a species even when it is present, and this can create significant limitations when fitting species distribution models. In this study, we aim to test the relevance of a mixed methodological approach that combines presence-only and presence-absence distribution models. We illustrate this approach using bottom trawl survey data to model the spatial distributions of 27 commercially targeted marine species. We use an environmentally- and geographically-weighted method to simulate pseudo-absence data. The species distributions are modelled using regression kriging, a technique that explicitly incorporates spatial dependence into predictions. Model outputs are then used to identify areas that met the conservation targets for the deployment of artificial anti-trawling reefs. To achieve this, we propose the use of a fuzzy logic framework that accounts for the uncertainty associated with different model predictions. For each species, the predictive accuracy of the model is classified as 'high'. A better result is observed when a large number of occurrences are used to develop the model. The map resulting from the fuzzy overlay shows that three main areas have a high level of agreement with the conservation criteria. These results align with expert opinion, confirming the relevance of the proposed methodology in this study. © 2013 Hattab et al.

Khemis I.B.,Instm Institute National Des Science Et Technologies Of La Mer | Gisbert E.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Alcaraz C.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Zouiten D.,Instm Institute National Des Science Et Technologies Of La Mer | And 4 more authors.
Aquaculture Research | Year: 2013

Allometric growth and ontogeny were studied in thick-lipped grey mullet Chelon labrosus reared in mesocosms from 1 to 71 day post hatching (dph). Multivariate allometric analysis of morphometric growth distinguished three distinct developmental stanzas separated by two morphometric metamorphosis lengths (Lm1 = 4.46 ± 0.06 mm; Lm2 = 28.56 ± 1.04 mm). Body mass growth also showed three distinct episodes separated by two inflections, correlated with morpho-functional changes. First episode concerned pre-flexion larvae and ended around 4.5 mm-LT (14-dph), coinciding with estimated Lm1. It was distinguished by reduced growth, but intense morphogenesis and differentiation processes. Organogenesis and allometric changes indicated that development priorities concerned feeding efficiency, by improving detection ability (sensory system development), ingestion capacity (head growth) and assimilation performance (digestive system differentiation), together with respiration efficiency (gill development). Second episode concerned post-flexion larvae and, ended around 8.6 mm-LT (25-dph). It was distinguished by fast growth of trunk and tail, acquisition of adult axial muscle distribution and completion of gill filament development, improving locomotion and oxygenation performances. It corresponded to transition towards metamorphosing stage as indicated by later isometric growth, musculature maturation and acquisition of juvenile phenotype. Metamorphosis seemed to end at Lm2, suggesting to avoid zootechnic handling before this size. © 2012 John Wiley & Sons Ltd.

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