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[The red crab or "langostilla", Pleuroncodes planipes is abundant in the Pacific coast upwelling system of Baja California. It feeds both on plankton in the pelagic realm and on detritus in the benthic habitat. Previous studies of stomach contents suggested variations with latitude and depth, and potential differences in productivity. The aim of this study was to use the lipid and astaxanthin contents as well as the fatty acid composition of the red crab as a measure of its nutritional condition and thus of the quality of their feeding areas. Crabs were collected in September 1991 using a shrimp trawl at 6 stations on the continental shelf off the west coast of Baja California between 26° and 24° N. All samples were sun-dried and homogenized by grinding, prior to the extraction of total lipids. Astaxanthin content was also measured at each location. The methyl esters of the total fatty acids were analysed by capillary gas chromatography with flame ionization detection (FID). Lipids and astaxanthin contents varied significantly from shallow to deeper locations, and both organic compounds were significantly correlated (p < 0.05). The C16 : 0, C16 : 1, C18 : 0, C18 : 1, C18 : 2n-6, C18 : 3n-3, C20 : 4n-6, C20 : 5n-3, and C22 : 6n-3 fatty acids were identified and quantified. The most abundant fatty acid was C20 : 5n-3, ranging from 8.3 to 21.06 g/100 g TL, followed by C16 : 0 (3.4-14.10 g/100 g TL) and the C20 : 4n-6 (1.42-7.43). Fatty acids with the least statistical variation between locations were C18 : 3n-3 and C20 : 5n-3. Fatty acids from the different locations were found to be grouped into a latitudinal cline, suggesting red crabs are good indicators of areas with distinct food quality. La langostilla o cangrejo rojo pelagico, Pleuroncodes planipes, es un abundante crustaceo decapodo del sistema de surgencias de la costa del Pacifico de Baja California. Se alimenta tanto en el habitat pelagico (de plankton) como en el bentonico donde consume principalmente detritus. Estudios previos de contenidos estomacales mostraron una variacion con la latitud y la profundidad, sugiriendo areas de distinta productividad. El objetivo de este estudio fue usar el contenido de lipidos, astaxantina y composicion de acidos grasos de la langostilla como reflejo de su condicion nutricional y de la potencial existencia de areas alimentacion especificas. El crustaceo fue colectado en septiembre 1991 usando una red camaronera sobre 6 sitios de la plataforma continental afuera de la Peninsula de Baja California entre los paralelos 26° y 24° N. Todas las muestras fueron secadas al sol y homogenizadas con molino antes de la extraccion de lipidos. El contenido de astaxantina se midio tambien en cada localidad. Los esteres metilicos del total de acidos grasos fueron obtenidos y analizados por cromatografia de gases con deteccion por ionizanon de flama. El contenido de lipidos y astaxantina vario significativamente de menor a mayor profundidad y ambos componentes mostraron correlaciones significativas (p < 0.05). Los acidos grasos C16 : 0, C16 : 1, C18 : 0, C18 : 1, C18 : 2n-6, C18 : 3n-3, C20 : 4n-6, C20 : 5n-3 y C22 : 6n-3 fueron identificados y cuantificados. El acido graso mas abundante fue C20 : 5n-3 que vario de 8.3 a 21.06 g/100 g de los lipidos totales, seguido de C16 : 0 (3.4-14.1 g/100 g LT) y el C20 : 4n-6 (1.42-7.43). Los acidos grasos con la menor variacion estadistica entre localidades fueron C18 : 3n-3 y C20 : 5n-3. Los acidos grasos de las distintas localidades se agruparon en una estructura de clinal latitudinal, sugiriendo que la langostilla es un buen indicador de la existencia de areas de distinta productividad y calidad de alimento., The red crab or "langostilla", Pleuroncodes planipes is abundant in the Pacific coast upwelling system of Baja California. It feeds both on plankton in the pelagic realm and on detritus in the benthic habitat. Previous studies of stomach contents suggested variations with latitude and depth, and potential differences in productivity. The aim of this study was to use the lipid and astaxanthin contents as well as the fatty acid composition of the red crab as a measure of its nutritional condition and thus of the quality of their feeding areas. Crabs were collected in September 1991 using a shrimp trawl at 6 stations on the continental shelf off the west coast of Baja California between 26° and 24° N. All samples were sun-dried and homogenized by grinding, prior to the extraction of total lipids. Astaxanthin content was also measured at each location. The methyl esters of the total fatty acids were analysed by capillary gas chromatography with flame ionization detection (FID). Lipids and astaxanthin contents varied significantly from shallow to deeper locations, and both organic compounds were significantly correlated (p < 0.05). The C16 : 0, C16 : 1, C18 : 0, C18 : 1, C18 : 2n-6, C18 : 3n-3, C20 : 4n-6, C20 : 5n-3, and C22 : 6n-3 fatty acids were identified and quantified. The most abundant fatty acid was C20 : 5n-3, ranging from 8.3 to 21.06 g/100 g TL, followed by C16 : 0 (3.4-14.10 g/100 g TL) and the C20 : 4n-6 (1.42-7.43). Fatty acids with the least statistical variation between locations were C18 : 3n-3 and C20 : 5n-3. Fatty acids from the different locations were found to be grouped into a latitudinal cline, suggesting red crabs are good indicators of areas with distinct food quality. La langostilla o cangrejo rojo pelagico, Pleuroncodes planipes, es un abundante crustaceo decapodo del sistema de surgencias de la costa del Pacifico de Baja California. Se alimenta tanto en el habitat pelagico (de plankton) como en el bentonico donde consume principalmente detritus. Estudios previos de contenidos estomacales mostraron una variacion con la latitud y la profundidad, sugiriendo areas de distinta productividad. El objetivo de este estudio fue usar el contenido de lipidos, astaxantina y composicion de acidos grasos de la langostilla como reflejo de su condicion nutricional y de la potencial existencia de areas alimentacion especificas. El crustaceo fue colectado en septiembre 1991 usando una red camaronera sobre 6 sitios de la plataforma continental afuera de la Peninsula de Baja California entre los paralelos 26° y 24° N. Todas las muestras fueron secadas al sol y homogenizadas con molino antes de la extraccion de lipidos. El contenido de astaxantina se midio tambien en cada localidad. Los esteres metilicos del total de acidos grasos fueron obtenidos y analizados por cromatografia de gases con deteccion por ionizanon de flama. El contenido de lipidos y astaxantina vario significativamente de menor a mayor profundidad y ambos componentes mostraron correlaciones significativas (p < 0.05). Los acidos grasos C16 : 0, C16 : 1, C18 : 0, C18 : 1, C18 : 2n-6, C18 : 3n-3, C20 : 4n-6, C20 : 5n-3 y C22 : 6n-3 fueron identificados y cuantificados. El acido graso mas abundante fue C20 : 5n-3 que vario de 8.3 a 21.06 g/100 g de los lipidos totales, seguido de C16 : 0 (3.4-14.1 g/100 g LT) y el C20 : 4n-6 (1.42-7.43). Los acidos grasos con la menor variacion estadistica entre localidades fueron C18 : 3n-3 y C20 : 5n-3. Los acidos grasos de las distintas localidades se agruparon en una estructura de clinal latitudinal, sugiriendo que la langostilla es un buen indicador de la existencia de areas de distinta productividad y calidad de alimento.]

Stomach contents of benthic red crabs (Pleuroncodes planipes) were analyzed to document number of items and composition. The crabs were captured along a series of latitudinal transects covering depths from 50 to 250 m, during March (12 stations) and September 1990 (8 stations). The number of food items decreased significantly from March to September at 150 and 200 m depth, the only strata compared since red crabs are usually absent from the coast above 100 m in summer. The particulate organic matter (POM) varied from 60 to 70% of total food items. The zooplankton fraction, mainly crustaceans, foraminiferans, and radiolarians, was second in importance. Phytoplankton was the next most important group, and was represented by 17 genera in March and 11 in September. The mean number of diatoms in stomachs per station decreased significantly (73.5 versus 7) from March to September. The number of genera/station showed the same pattern (5.36 versus 3.6). The most abundant (number of cells) and frequent (presence over number of stations) diatom genera in March were Nitzschia, Melosira and Cocconeis in that order, accounting for 74% of the relative importance index. In September, Cyclotella, Nitzschia and Melosira accounted for 42% of the importance index. The stomach contents in benthic red crabs indicate a decreasing availability of food in the area from winter-spring through the summer. This pattern correlates well with the diminishing intensity of the coastal upwelling system and weakening of the California Current. The amount of stomach contents in red crabs decreased as the density of the crustacean species increased.

Le galatheide pelagique Pleuroncodes planipes est tres abondant au large des cotes occidentales de Basse-Californie. Afin de determiner les changements saisonniers possibles dans la frequence et la biomasse de ces crustaces sur le plateau continental, ou se tient une grande partie de la population, une recherche a long terme a ete entreprise, incluant la surveillance de son abondance. C'est au total 198 chalutages sur le fond, avec des filets a crevettes, qui ont ete effectues de juillet 1987 a septembre 1990, couvrant ainsi toutes les saisons. Les crustaces etaient presents sur tout le plateau continental en hiver et au printemps (au moment de la reproduction). Une abondance moyenne maximale de 450 kg/Ha a ete atteinte a la fin du printemps, a 51-100 m de profondeur. Quand la temperature au fond montait jusqu'a 16°C (ete-automne), frequence et abondance decroissaient l'une et l'autre a tous les niveaux, avec une disparition complete au-dessus de 50 m de profondeur. Ce n'est qu'a plus de 151 m que la frequence de Pleuroncodes etait relativement haute. L'abondance decroissait en ete dans les profondeurs de moins de 100 m (0-200 kg/Ha), alors qu'elle croissait entre 100-200 m (400 kg/Ha). Les presentes observations suggerent que les adultes ont un cycle migratoire: ils gagnent les eaux plus profondes au printemps et en ete pour revenir occuper la totalite du plateau continental en hiver. Pendant l'ete Pleuroncodes s'etend aussi vers le talus continental, jusqu'a 500 m au moins. Les crustaces occupent egalement le fond et la colonne d'eau, de nuit comme de jour, en depit des mouvements nocturnes signales du fond vers la surface.