Horizontal and vertical movements of the common dolphinfish (Coryphaena hippurus) in La Paz Bay, Mexico

Abstract

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...

Dolphinfish Movements in the Eastern Pacific Ocean of Mexico Using Conventional and Electronic Tags

“…Although only "reverse" diel diving (deeper dives at night) has been observed in other dolphin sh studies 25,36,17,27,26 , this study observed both "traditional" (deeper dives during daytime) and reverse diel diving, even within the records of a single sh. This plasticity in habitat utilization patterns was similar in sh across regions and sexes, and thus may be a result of ephemeral differences in the thermal structure of the water column, presence or absence of predators, and/or changes in the distribution and availability of prey items.…”

“…In terms of vertical movements, short duration tagging studies in both the western central Atlantic and western Paci c Oceans report diel shifts in behavior from shallow depths during the day to deeper depths (i.e., below the surface isothermal layer) at night, perhaps in response to movements of epipelagic and mesopelagic prey, or to reduce risk of predation 25,26 . The same diel vertical behavior was noted in both farm-reared and wild dolphin sh in marginal waters of the East China Sea 27 .…”

Dolphinfish Movements in the Eastern Pacific Ocean of Mexico Using Conventional and Electronic Tags

“…Although only "reverse" diel diving (deeper dives at night) has been observed in other dolphin sh studies 18,[25][26][27][28]37 , the "traditional" diel diving observed here may be a result of ephemeral changes in the thermal structure of the water column, presence or absence of predators, and/or changes in the distribution and availability of prey items. It is also possible that the longer duration tag deployments in this study reveal a plasticity and variability in movements not observed in previous studies with shorter tag deployments.…”

“…In terms of vertical movements, short duration tagging studies in the western central Atlantic Ocean, western Paci c Ocean, and the Gulf of California, Mexico report diel shifts in behavior from shallow depths during the day to deeper depths (i.e., below the surface isothermal layer) at night, perhaps in response to movements of epipelagic and mesopelagic prey, or to reduce risk of predation 18,[25][26][27] .The same diel vertical behavior was noted in both farm-reared and wild dolphin sh in marginal waters of the East China Sea 28 . In the oceanic waters of the EPO, long-term sheries-independent observations of seasonal, horizontal and vertical movement patterns of dolphin sh have not been described to date.…”

“…Therefore, data archived during tag deployments were either subsampled or summarized, transmitted post-release via satellites and accessed via the Wildlife ComputersÒ data portal (mywildlifecomputers.com). Data strings of temperature and depth time-series were subsampled from the archival data and transmitted in packets of ten data points per 150 seconds; binned summaries of time-at-depth [0,5,10,15,20,30,40,50,75,100,150,>150 meters] and time-at-temperature[4,16,18,20,22,24,26,27,28,29,30,>30 °C] used 12 bins to bound and center sh depth and temperature utilization, respectively (e.g., see Additional File 1). Light and mixed layer temperature daily summaries were transmitted using default settings.…”