Migratory history of the spotted flagtail, Kuhlia marginata

Abstract

The spotted flagtail, Kuhlia marginata (Kuhliidae) is commonly found in streams throughout the Ryukyu Archipelago, including Okinawa Island, Japan. Although it has been suggested that they spawn at sea, little is known about their migratory history. The aim of the study was to clarify their migration history based on otolith microchemistry analysis, size composition and the gonadal development of fish collected from the Genka River on Okinawa Island. All strontium/calcium (Sr/Ca) ratios of otoliths remained high around their cores, and then dropped rapidly at some distance from the core. The estimated standard length corresponding to decreases correlated with the size of new recruits collected in the river (ca. 20 mm in standard length: SL). Multiple increases, the sign for migrations into the high saline area, were recognized intermittently around the otolith margin. As the estimated SL at these increases in the Sr/ Ca ratio occurred above the minimum maturation size (female: 95.5 mm SL; male: 83.5 mm SL), such multiple increases in Sr/Ca ratios were caused by spawning migration. Therefore, we conclude that the catadromous pattern of K. marginata is as follows; this species grows in the sea during the early life stage until ca. 20 mm SL and then grow in the freshwater area until maturation, before they migrate again to the sea for spawning. Sr/Ca ratio profiles also suggested that a large number of males did not return to the freshwater area after spawning, whereas females might spawn several times during their lives around the inshore area.

Evidence of diadromy in the French Polynesian Kuhlia malo (Teleostei: Percoidei) inferred from otolith microchemistry analysis

“…We inferred that this otolith elemental signature (Sr/Ca approximately 5 mg·g −1 , Ba/Ca approximately 4 μg·g −1 ) was associated with the marine environment encountered during the early life of all individuals sampled. The Sr/Ca ratios found here were similar to those found by Oka & Tachihara (2008), which they attributed to larval growth at sea. Moreover, Campana (1999) reported a mean Sr/Ca ratio of 5.3 mg·g −1 for 43 marine species.…”

“…Two calcium carbonate standards containing trace elements in expected concentrations of 100 and 500 lgAEg )1 were prepared by pressing 20 mg of dried precipitate prepared by the method of Barats et al (2007) into 3-mm-diameter dies at a pressure of 0.5 t for 2 min. Moreover, the fish otolith certified reference material no 22 (National Institute for Environmental Studies, Japan) (Yoshinaga et al 2000) was pelletised using the same protocol and used to assess the reliability of the CaCO 3 pellets and also to match the high Sr concentrations (>2000 lgAEg )1 ) that were predicted to be found in K. malo otoliths, assuming this species undergoes marine migrations similar to Kuhlia xenura and K. marginata (Benson & Fitzsimons 2002;Oka & Tachihara 2008). 43 Ca was used as an internal standard for each ablation to check for variation in ablation yield.…”

“…Species of this genus occur in seawater and freshwater habitats (Regan 1913; Senou 1989). Two freshwater species, Kuhlia marginata (Cuvier 1829) and Kuhlia rupestris (Lacépède 1802) are considered to be catadromous (Hogan & Nicholson 1987; Oka & Tachihara 2001, 2008). Four species are reported in French Polynesia: Kuhlia mugil (Forster, 1801), Kuhlia sandvicensis (Steindachner, 1876) and Kuhlia petiti (Schultz, 1943) are marine species and Kuhlia malo (Valenciennes, 1831), which is the only one found in streams of this archipelago, is presumed to be diadromous, but no studies have been published on its life history.…”