Swimming depth of dolphinfish (Coryphaena hippurus) associated and unassociated with fish aggregating devices

Abstract

Abstract-Dolphinfish (Coryphaena hippurus), large pelagic predators and important fishery targets, frequently associate with floating debris or manmade fish aggregating devices (FADs). We tagged 8 dolphinfish with pressure-sensitive ultrasonic transmitters and actively tracked individuals continuously for up to 40 h to elucidate the vertical movement patterns and differences between FADassociated (FAD-A) and FAD-unassociated (FAD-U) fish. Four additional fish were equipped with acoustic transmitters and passively monitored for several days with receivers attached to FADs. When not associated with FADs, dolphinfish used the upper 75-100 m of the water column during the day and made descents up to 160 m during the night. In contrast, FAD-A fish generally stayed within the upper 10 m of the water column and tended to make deeper excursions during the day rather than at night. Water temperature data from expendable bathythermographs deployed during active tracking showed that fish only descended to depths where temperatures were ≤3°C cooler than the uniform-temperature surface layer. The use of vertical behavior to determine whether a dolphinfish is associated or not with a floating object opens the possibility for new, large-scale research aimed at investigating the role of floating objects in the ecosystem inhabited by this species and at assessing the impacts of FADs on its ecology.

Use of video monitoring to quantify spatial and temporal patterns in fishing activity across sectors at moored fish aggregating devices off Puerto Rico

“…If similar instruments are deployed on FADs equipped with video cameras, the amount and change in biomass of fish aggregating around the FADs (Freon andDagorn 2000, Girard et al 2004) could be related to fishing activity. In addition, fishing activity could be compared with the diel movements of fish at FADs (see, Dagorn et al 2007, Taquet et al 2008, Whitney et al 2016) and compared with catch reports to allow estimates of when specific species may be more vulnerable to fishing. These strategies could provide fishers with information to adapt fishing strategies by TOD and managers to estimate fishing mortality and biomass depletion.…”

Movement Patterns of Atlantic Tarpon (Megalops atlanticus) in Brewers Bay, St. Thomas US Virgin Islands

“…Many coastal pelagic sh, such as barracuda (S. barracuda), white marlin (K. albida), dolphin sh (C. hippurus) and many species of tuna show similar vertical movement patterns, where they spend the majority of time at shallow depths or close to the surface and then make diel/seasonal deep water movements [62][63][64].…”

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

“…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. Light and mixed layer temperature daily summaries were transmitted using default settings.…”

“…Additional studies have documented that dolphin sh strongly associated with oating surface macroalgae, otsam, and Fish Aggregating Devices (FADs), with both homing and high levels of delity (>15 days) observed in the Indian Ocean [18][19][20][21][22][23] . A study combining commercial and recreational sheries data determined that while sea surface temperature is a strong correlate of dolphin sh catches, surface chlorophyll-a is not 24 .…”