Search

Current data suggest that lobster (Homarus americanus) populations are less homogenous than once believed. In an effort to better discriminate morphologically among lobsters from different sites, we developed a photographic method using ImageJ and compared it with commonly used 'hand' measurements. We standardized the measuring process using a strap-down board for both dorsal and ventral photographs with a camera mounted at a fixed position above the lobster. Discriminant analysis showed that both hand and photographic methods were useful in discriminating lobsters--both males and females--from three different sites. Additionally, the photographic method improved reproducibility and resolution, it reduced measurement time at the dock, and it created a permanent record for later verification, additional statistical analyses, and observer training. Les donnees actuellement disponibles portent a croire que les populations de homards (Homarus americanus) sont moins homogenes que l'on ne le pensait. Afin d'en arriver a une meilleure discrimination morphologique de homards provenant de lieux differents, nous avons mis au point une methode photographique appelee ImageJ et l'avons comparee a des approaches <> de mesure couramment employees. Nous avons normalise le processus de mesure en utilisant une planche munie d'attaches pour la prise de photographies dorsales et ventrales a l'aide d'un appareil-photo installe a hauteur fixe au-dessus du homard. L'analyse discriminante a demontre l'utilite des methodes tant manuelle que photographique pour la discrimination de homards tant males que femelles provenant de trois sites differents. La methode photographique a en outre ameliore la reproductibilite et la resolution, reduit le temps de mesure au quai et produit un registre permanent pouvant etre utilise pour des verifications ulterieures, d'autres analyses statistiques et la formation d'observateurs. [Traduit par la Redaction], Introduction The phenotype of an organism can provide insight into its habitat and behavior. Morphometrics, the analysis of shape, applies multivariate methods to lengths, widths, and angles. Morphometric analyses using [...]

ABSTRACT Epizootic shell disease in the American lobster, Homarus americanus, is seriously affecting inshore populations in southern New England. The disease can change the biochemical profile of lobsters and could [...]

Using massively parallel sequencing data from two species with different life history traits, American lobster ( Homarus americanus) and Arctic Char ( Salvelinus alpinus), we highlight how an unbalanced sex ratio in the samples and a few sex-linked markers may lead to false interpretations of population structure and thus to potentially erroneous management recommendations. Here, multivariate analyses revealed two genetic clusters separating samples by sex instead of by expected spatial variation: inshore and offshore locations in lobster, or east and west locations in Arctic Char. To further investigate this, we created several subsamples artificially varying the sex ratio in the inshore/offshore and east/west groups and then demonstrated that significant genetic differentiation could be observed despite panmixia in lobster, and that FST values were overestimated in Arctic Char. This pattern was due to 12 and 94 sex-linked markers driving differentiation for lobster and Arctic Char, respectively. Removing sex-linked markers led to nonsignificant genetic structure in lobster and a more accurate estimation of FST in Arctic Char. The locations of these markers and putative identities of genes containing or nearby the markers were determined using available transcriptomic and genomic data, and this provided new information related to sex determination in both species. Given that only 9.6% of all marine/diadromous population genomic studies to date have reported sex information, we urge researchers to collect and consider individual sex information. Sex information is therefore relevant for avoiding unexpected biases due to sex-linked markers as well as for improving our knowledge of sex determination systems in nonmodel species. [ABSTRACT FROM AUTHOR]

Current data suggest that lobster ( Homarus americanus) populations are less homogenous than once believed. In an effort to better discriminate morphologically among lobsters from different sites, we developed a photographic method using ImageJ and compared it with commonly used 'hand' measurements. We standardized the measuring process using a strap-down board for both dorsal and ventral photographs with a camera mounted at a fixed position above the lobster. Discriminant analysis showed that both hand and photographic methods were useful in discriminating lobsters - both males and females - from three different sites. Additionally, the photographic method improved reproducibility and resolution, it reduced measurement time at the dock, and it created a permanent record for later verification, additional statistical analyses, and observer training. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)