Determination of Temporal Spawning Patterns and Hatching Time in Response to Temperature of Atlantic Bluefin Tuna (Thunnus thynnus) in the Western Mediterranean

Abstract

This study analysed the temporal pattern of Atlantic bluefin tuna (ABFT) spawning in the Balearic spawning ground and examined its reproductive performance after years in captivity. Furthermore, ABFT hatching time at different on-site temperatures was determined for the first time. Spawning surveys were carried out in 4 spawning seasons (2009–2012) aboard tuna transport vessels. Three groups of spawners were monitored: a captive group transported to the spawning region and monitored throughout the four spawning seasons and two wild groups caught in 2009 and 2010 which were transferred to a monitoring transport cage immediately after being caught. Surface plankton samples were collected nightly, beginning immediately after the first purse seine catches were made and concluding after spawning was observed to have ended. All groups displayed the same spawning hours, restricted between 2:00–5:00 a.m. The captive group, as they got older, shifted towards the earliest hour, suggesting an age influence on reproductive time. The onset of spawning varied annually from the end of May to the beginning of June at temperatures around 19°C–20°C, ending by the second week of July. The peak of spawning was consistently around the summer solstice, June 15th–30th. The results showed the negative effect of unstable oceanographic conditions in the spawning process which might influence the annual reproductive success of ABFT. The influence of temperature on hatching time was higher than that observed in other tuna species, twice as fast at 26°C (23 h) as at 19.5°C (49 h). Overall, this study shows the strength of the internal mechanism in ABFT that controls spawning traits. Spawning in ABFT is cyclical and highly synchronised on diel and annual scales. We consider that the timing of spawning is rather influenced by day length and its adaptive significance is discussed.

Modeling environmental influence on Atlantic bluefin tuna bycatch by Mexican longliners in the Gulf of Mexico

“…Arrizabalaga et al () also found these environmental preferences for BFT species in a broad study covering the Atlantic, Pacific, and Indian oceans. Even though the preferential thermal range derived from the model was much lower than the recognized spawning temperature threshold of 24°C (Schaefer, ), recent estimations set the thermal conditions of the spawning season onset closer to our results (Alemany et al, ; Gordoa & Carreras, ; Reglero, Balbín, et al, ; Reglero, Ortega, et al, ). In addition, greater BCPUEs were found related to negative SLA, an indicator of mesoscale cyclonic eddies, which associated with increased productivity (Biggs & Muller‐Karger, ; Gasca, ) have been recognized as key areas for reproduction and recruitment of many fish species (Bakun, ; Condie & Condie, ; Condie, Mansbridge, & Cahill, ).…”

Solar and lunar influences on the spawning activity of Pacific bluefin tuna (Thunnus orientalis) in the south‐western North Pacific spawning ground

“…Lunar‐related spawning has not been previously reported in Pacific bluefin tuna, and may be due to 10 day aggregated analyses for the occurrence of POFs (Ashida et al., ; Chen et al., ). A lunar effect on spawning activity has also not been reported for any other Thunnus species, apart from captive fish (Gordoa & Carreras, ; Margulies et al., ). Although not definitive, spawning effort of captive yellowfin tuna Thunnus albacares increases just prior to a full moon (Margulies et al., ), and the beginning of spawning for wild captured and caged Atlantic bluefin tuna was reported to coincide with a date around a full moon (Gordoa & Carreras, ).…”

“…Instead, a solar calendar date was used in the present study as a factor likely implying a temperature effect. The spawning peak of Atlantic bluefin tuna in the Mediterranean is reported to be around the summer solstice (15–30 June; Gordoa & Carreras, ), and implies that the solar calendar date is an alternate factor to predict spawning activity. A solar calendar date is a better factor to predict future spawning activity and make an appropriate harvest control plan for Pacific bluefin tuna than temperature, which has low predictability.…”

Variability of preferred environmental conditions for Atlantic bluefin tuna (Thunnus thynnus) larvae in the Gulf of Mexico during 1993–2011

“…While certain environmental parameters, such as temperature, may provide the baseline for a successful spawning season and for how long it takes for eggs to hatch (Medina et al ., ; Gordoa and Carreras, ), the actual spawning behavior, survival of larvae and subsequent recruitment of bluefin tuna is determined by multiple processes. Drivers of bluefin tuna larvae survival are not generally well known, and it is assumed that mortality during early life is primarily due to starvation and predation (Rooker et al ., ), both of which are dependent on various biophysical processes.…”