Recognising mollusc shell contours with enlarged spines: Wavelet vs Elliptic Fourier analyses

Gastropod shells may present large spines and sharp shapes that vary according to environmental, taxonomic, and evolutionary factors. In these cases, classic morphometric methods used to study shell contour might not provide a clear representation of morphological shell based on angular decomposition of contour. The present study analyzed and compared for the first time the robustness of the contour analysis using wavelet transformed and Elliptic Fourier descriptors for gastropod shells including enlarged spines. For that, we analyzed two geographical and ecological separated populations of Bolinus brandaris from the NW Mediterranean Sea. Results showed that contour analysis of gastropod shells with enlarged spines can be analyzed using both methodologies, but the wavelet analysis provided a better local discrimination. From an ecological perspective, shells with spines of different sizes were observed in both localities suggesting a wide plasticity of the specie

Canary 2019-updating highlights

Small pelagic fishery in the Canary Islands is carried out by an interannual quite variable artisanal fleet of purse-seiners. Total landings produced by the Canary purse-seiners have experienced a decrease from 2017–2019. However, it is not the case for the Atlantic chub mackerel, which not only is the main of the four species targeted by this fleet (>50%), but whose landings have increased since 2014, with European sardine and sardinellas almost absent in 2019. Concerning the length frequencies present in landings, the most relevant observation is that a noticeable increase in the modal lengths has been registered since the beginning of the monitoring programme in 2013, from around 22 cm to individuals ≥27 cm in 2019. Regarding ongoing studies, a new work has been launched based on the otolith shape analysis of a sizable sample comprising 792 otoliths corresponding to a time period from August 2016 to December 2017. A DIvisive ANAlysis (DIANA) Clustering method using the 4th wavelet obtained from otolith contours resulted in the detection of five different morphotypes or otolith phenotypes. Differences were found mainly in the collicum-antirostrum and the dorsal margin areas of the otolith contours. Two of the morphotypes represents 85% of the samples analysed, whose individuals were slightly larger than the other morphotypes, considering mean lengths (≥25 cm vs ≤24.5 cm). These very preliminary results open many future questions to be explored: 1. Do these results suggest intraspecific variation in the growth rate among phenotypes? 2. Do phenotypes proportions change in relation to seasonal variations? 3. May exist different ecological strategies related to each phenotypes? and 4. Are these otolith phenotypes present in other geographical areas

Taxonomic diversity hidden inside the mantle of Octopus vulgaris: valuable source of information

The common octopus, Octopus vulgaris, is a very important demersal fishery resource targeted, among other fleets, by freezer bottom-trawlers in the Mauritanian Economic Exclusive Zone (MEEZ). From August 2010 to September 2011, a total of 1696 octopuses caught in the MEEZ where analysed. Many organisms trapped into the octopuses' mantle were found and identified, which are jointly swept while the trawling catches the targeted species. A latitudinal (by ecoregion) and depth study was performed to determine differences in the taxonomic diversity of these hidden organisms. The findings showed that the diversity patterns were similar to already established in the area based on scientific surveys. Therefore, this ignored bycatch could provide complementary ecological information of the habitat of O. vulgaris.En prensa0,36

Using Otolith Phenotipic Variability to Infer Potential Population Differences of Scomber colias in the Northeast Atlantic and Mediterranean Sea

In the last decade there has been a growing interest in the Atlantic chub mackerel, Scomber colias, due to a noticeable expansion of this species in the East Atlantic Ocean from areas of greater abundance off northwest Africa to Atlantic Iberian waters and the Mediterranean Sea (ICES, 2021). To implement sustainable management measures in the current global warming situation it is crucial not only to identify biologically-meaningful management units, but also to understand otolith morphological variability along its geographic distribution areas. We analysed the otolith shape variability in S. colias considering four origins in as one metapopulation.FEM

Adaptive plasticity of otolith shape in Scomber colias from the Canary Islands

Small pelagic fish in the Canary Islands (CE Atlantic, from 29°27'N to 27°37'N and from 18°12'W to 13°17’W) are mainly targeted by artisanal purse-seiners, whose activity is monitored by the Canary Oceanographic Centre (IEO-CSIC) in the Data Collection Framework since 2013. The Atlantic chub mackerel (Scomber colias) is the main of the four species targeted by this fleet (45% of the total landings), with landings quite stable around a mean value of 850 tons/year. From August 2016 to December 2017, 792 otoliths of S. colias corresponding to monthly analyses of the mentioned fleet’s landings have been launched used to identify the potential presence of different morphotypes inhabiting Canary waters, based on otolith shape analysis. A DIvisive ANAlysis (DIANA) Clustering method using the 4th wavelet obtained from otolith contours resulted in the detection of five different morphotypes or otolith phenotypes. Differences where found mainly in the collicum-antirostrum and the dorsal margin areas of the otoliths’ contours. Two of the morphotypes represented 85% of the samples analyzed, whose individuals were slightly larger than the other morphotypes, considering mean lengths (≥25cm vs. ≤24.5cm). These very preliminary results open many future questions to be explored: 1) Do these results suggest intra-specific variation in the growth rate among phenotypes?; 2) Do phenotypes proportions change in relation to seasonal variations?; 3) May exist different ecological strategies related to each phenotypes?; and 4) Are these otolith phenotypes present in other geographical areas?FEM