Swimming behaviour and migration of a swordfish recorded by an archival tag

Abstract

An archival tag equipped with sensors for temperature, depth and luminous intensity is an excellent method to elucidate behaviour and migration of marine organisms. Herein, what we believe is the first successful archival tag experiment with swordfish in the world is reported. The swordfish, which was harpooned with an archival tag encased in a plastic capsule, was released in July 1999 off the east coast of Japan. The fish was recaptured by a harpoon fishing vessel in June 2000, only 103 km from the tagging location and weighed approximately 120-kg. By comparing the water temperature data of the archival tag with oceanographic data, a cyclic seasonal migration between the food-rich Oyashio cold current area (40-45 • N) during summer and the subtropical wintering area (10-20 • N) was suggested. During most of the days of observation and for the majority of the time within a day, tagged fish swam in cold water (3-6 • C) and deeper than approximately 200 m; at night, fish generally stayed near the warmer surface waters (21-27 • C). The greatest swimming depth was approximated to be 900 m, deduced from ambient water temperature data. The swimming depth and behaviour pattern changed in response to the ambient water temperature.Extra keywords: diel patterns, vertical distribution, water temperature Xiphias gladius.

Description of diet of pelagic fish in the southwestern Atlantic, Brazil

“…The organisms identified as the food items of X. gladius may corroborate the assumption about the daily vertical displacement pattern presented by the individuals of this species, which has been described by Carey & Robison (1981) and Takahashi et al (2003). Such a fact could be evaluated in this way by the reason that both mesopelagic and epipelagic (Myctophidae in general and Ommastrephidae) were commonly found within the fish stomachs, as happened to Brama sp., Auxis sp.…”

Genetic population structure of the Swordfish (Xiphias gladius) in the southwest Indian Ocean: Sex-biased differentiation, congruency between markers and its incidence in a way of stock assessment

“…In contrast males appear to remain more abundant in tropical regions and rarely undertake long-distance migrations observed for females (De Martini et al, 2000;Palko et al, 1981). Tag-recapture experiments showed that even if some swordfish are able to undertake long-distance inter-ocean movements (at the scale of an ocean; Sedberry and Loefer, 2001;Takahashi et al, 2003), 20% of tagged swordfish are recaptured close to the point of release, revealing important inter-individual plasticity in migrating behaviour and suggesting residency or homing behaviour for some individuals within specific regions (Sedberry and Loefer, 2001). Thus, considering dispersal of the swordfish, it may exist great disparities between the maximal dispersal range (mainly linked with feeding behaviour) and the reproductive effective dispersal range (more important in term of population replenishment and structure).…”

An evaluation of resource partitioning between two billfish, Tetrapturus belone and Xiphias gladius, in the central Mediterranean Sea

“…Fish were mainly represented by Trichiurudae & Robinson, 1981;Takahashi et al, 2003), these Ommastrephidae are generally preyed upon at nighttime, when they migrate to the surface. Moreover, the low values of both Schoener and Horn overlap indices also underlined food partitioning between the two species, which avoid competitive exclusion.…”