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ABSTRACT. The common dolphinfish (Coryphaena hippurus) is an important resource for the sport-fishing industry in Mexico. It is captured incidentally by the eastern Pacific purse-seine tuna fishery and in coastal areas by artisanal fisheries. Although it is considered a highly migratory species, only few studies of its movements are available. In this study, the behavior of the common dolphinfish was analyzed by means of acoustic telemetry at three locations within La Paz Bay (southern Gulf of California) from summer to autumn 2013. Acoustic transmitters were attached to six individuals and they were tracked for periods of up to 48 h. Every hour, vertical profiles of temperature and bathymetry were made. To determine the effect of biotic (sex) and abiotic (water temperature and depth, thermocline depth, hour, and bathymetry) variables on the horizontal and vertical movements of tagged organisms, generalized additive mixed models were applied. The results showed a tendency of horizontal movements to the southwestern zone of the bay; two individuals crossed from the eastern to the western side. The average speed was 0.51 m s -1 . The vertical movements showed that the individuals spent 80% of the time above 34 m depth, of which around 45% was spent in the upper 10 m of the water column. During daylight hours they swam in shallow waters (upper 10 m) and at night they performed deeper dives (73 m maximum depth). Biotic and abiotic variables influenced both types of movements; however, bathymetry and temperature largely explained fish movements.Key words: horizontal and vertical movements, Coryphaena hippurus, La Paz Bay, acoustic transmitters. RESUMEN.El dorado (Coryphaena hippurus) es un recurso importante para la pesca deportiva en México. Es capturado incidentalmente por la flota atunera de cerco en el Pacífico oriental y en áreas costeras por la pesca artesanal. Aunque es considerada una especie altamente migratoria, existen pocos estudios sobre sus movimientos. En este estudio se analizaron los movimientos del dorado por medio de telemetría acústica en tres localidades dentro de la bahía de La Paz, parte sur del golfo de California, entre verano y otoño de 2013. Se adhirieron transmisores acústicos a seis individuos y se siguieron durante periodos de hasta 48 h. Cada hora, se hicieron perfiles verticales de temperatura y batimetría. Para determinar el efecto de variables bióticas (sexo) y abióticas (temperatura y profundidad del agua, profundidad de la termoclina, hora y batimetría) sobre los movimientos horizontales y verticales de los organismos marcados, se aplicaron modelos aditivos generalizados mixtos. Los resultados mostraron una tendencia a movimientos horizontales a la zona suroeste de bahía de La Paz; dos movimientos atravesaron la bahía de sureste a suroeste. La velocidad promedio fue de 0.51 m s -1 . Los movimientos verticales indicaron que los individuos estuvieron por encima de los 34 m de profundidad el 80% del tiempo, del cual aproximadamente 45% estuvieron en los 10 m superiores. En horas de lu...

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We analyzed individual growth and body mass allometry of the temperate stock of Sardinops sagax from samples collected on commercial fleet during 2005 to 2014 in the southern California Current System. Ages were estimated on otolith growth ring reading. Age (years) and standard length (SL; mm) data were fitted using four growth models: von Bertalanffy (VBM), Gompertz (GM), logistic (LM), and Schnute (SM) models. Parameters of each model were calculated by the maximum likelihood method using Akaike information criterion and Akaike’s weight (WAICi) to select the model with the greatest plausibility. Additionally, the interannual growth performance (φ′) variation was described. Body mass allometry was established from the relationship between total body mass (TM; g) and standard length. The sardine samples ranged in size from 114 to 226 mm SL and in weight from 20 to 192 g TM; ages varied from 0.5 to 6.0 years. The allometric parameter (b) was estimated to be 3.155 (3.154–3.156), showing a hyper-allometry growth type. On the basis of raw data, we found that the LM model fit the original data better (WAICi ~35%). When models were fitted to data bolstered with simulated values, the VBM model obtained the greatest weight (WAICi = 60.9%), but the LM model had null plausibility. Consequently, we determined that the Pacific sardine growth pattern was best described by the VBM model, which appears to be more robust against biased data. The φ′ showed interannual variation (2.13–2.51), with an average of φ′ = 2.25. An apparent inverse relationship was observed between φ′ and the Oceanic Niño Index (ONI) or the Pacific Decadal Oscillation (PDO) and the apparent positive relationship between Upwelling Index (UI) and φ’.

Background. The leopard grouper, Mycteroperca rosacea (Streets, 1877), is endemic to northwestern Mexico and has high commercial value. Although facts of its basic biology are known, information on its trophic ecology, in particular, is scarce. The objective of the presently reported study was to characterize the feeding habits of M. rosacea through the analysis of stomach contents, and to determine possible variations linked to sex (male or female), size (small, medium, or large), or season (spring, summer, autumn, or winter), in order to understand the trophic role that this species plays in the ecosystem where it is found. Materials and methods. Fish were captured monthly, from March 2014 to May 2015 by spearfishing in Santa Rosalía, BCS, Mexico. Percentages by the number, by weight, and frequency of appearance of each food category, the index of relative importance (%IRI), and prey-specific index of relative importance (%PSIRI) were used to determine the importance of each prey item in the leopard grouper diet. Diet breadth was calculated using Levin's index. Possible differences in the diet by sex, size, or season were identified through a multivariate PERMANOVA analysis. Results. A total of 341 leopard grouper specimens were collected, 309 of which had stomachs containing food. A total of 28 prey species were identified. According to the %IRI, the contribution to the diet of the coastal pelagic prey Nyctiphanes simplex and Sardinops sagax (Jenyns, 1842) was 87%, whereas according to the %PSIRI the contribution to the diet of those two prey species was 57%, in addition to several demersal prey species. A PERMANOVA analysis indicated that there were significant differences in the diet of leopard grouper by sex, size, and season, but the interactions sex-size, sex-season, size-season, and sex-size-season, were not significant. Conclusions. Mycteroperca rosacea was identified as a carnivorous predator with narrow trophic width, with significant differences in diet according to the sex, size, season, and size-sex interactions, which could be the result of different energetic requirements, hunting abilities, and food availability. The %PSIRI turned out to be the most adequate index to determine the feeding habits of fish, as it provides a better mean value to determine the most important prey.

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