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...

The description of the movements and habitat preference of marine fishes is essential to understand their biology and in the evaluation of commercially exploited species and the conservation of endangered ones. In this regard, little is known about the movements of the totoaba (Totoaba macdonaldi), despite its being listed as critically endangered and having been a relevant fishery resource in the past century in Mexico. Totoaba is a fish species endemic to the Gulf of California characterized by late maturation, prolonged life and annual reproduction. Totoaba has maintained its known historical distribution range, although its movements and habitat occupancy in the water column have remained poorly understood. The present study describes, for the first time and at a daily fine scale, the vertical movements and habitat preferences of the totoaba in the Upper Gulf of California. Pop-up satellite archival tags (PSATs) were used to record depth and temperature at 4-minute intervals. Ten individuals were caught and tagged in May 2016 in the Upper Gulf of California and Colorado River Delta Biosphere Reserve. All PSATs were either prematurely released or lost. Data derived from two recovered tags that saved data for 43 and 75 tracking days, respectively, were analysed. The results showed that tagged fishes moved southward to the vicinity of Angel de la Guarda Island; these are consistent with spatial displacement patterns reported in the literature, with a linear displacement of 223 km from deployment to pop-up sites. Fish spent 47% of the time within a depth range of 25–35 m. Depth increased to 70 m for one fish in early summer (late June). The preferred temperature of fishes ranged between 21–23°C. A generalized linear model revealed that vertical movement was influenced by temperature. The vertical displacement of the totoaba shows a diurnal variation that may be associated with the distribution of its prey. Further work is needed to test this hypothesis with a larger number of organisms.