Seasonality of spawning by tropical anguillid eels around Sulawesi Island, Indonesia

Abstract

Remarkably little is known about the life histories of the many tropical anguillid eels distributed across the Indo-Pacific region, and since the Danish expedition to study eels in the region in 1928 and 1929, research on these eels has only begun again in recent years. Sampling for anguillid leptocephali in the Indonesian Seas has been carried out recently to learn about the spawning ecology and larval distributions of tropical eels there. The leptocephali of Anguilla marmorata, Anguilla bicolor pacifica, Anguilla borneensis, Anguilla interioris, and Anguilla celebesensis were collected around Sulawesi Island both in May 2001 and October of 2002. The development of genetic identification techniques has enabled these leptocephali to be identified to species, and their distributions and sizes during different seasons indicated that there are differing life history patterns among sympatric species in the region. A. celebesensis was found to have been spawning in Tomini Bay of northeastern Sulawesi Island in March and April 2001, but apparently, no spawning had occurred in the late summer and fall of 2002. Studies on anguillid glass eels have suggested that tropical anguillids may spawn throughout much of year, but our research on leptocephali in Tomini Bay and data on the downstream migration of tropical anguillids in the major tributary to Tomini Bay indicate that A. celebesensis may have a distinct seasonal pattern of spawning possibly related to the regional monsoon cycles. This is the first evidence of seasonality of spawning in tropical anguillid eels whose life histories are only just beginning to be revealed.

The ecology of oceanic dispersal and survival of anguillid leptocephali

“…The sampling surveys conducted in the northern Indonesian Seas region have indicated that anguillid leptocephali are usually present but not at high abundances. This was the case in the Danish survey (Jespersen 1942) and during recent surveys (Aoyama et al 2003;Kuroki et al 2006;Wouthuyzen et al 2009) (Fig. 6).…”

“…It has also been realized that some tropical anguillids can spawn locally over deepwater basins (Aoyama et al 2003) and that tropical eels have shorter larval durations, faster growth, and a smaller maximum larval size than temperate species (Kuroki et al 2014). So the dispersal of anguillid eel larvae can range from the retention of A. celebesensis leptocephali within the small Tomini Bay of Sulawesi Island for about 3 months (Aoyama et al 2003;Wouthuyzen et al 2009;Kuroki et al 2014) to the dispersal of European eel leptocephali all across the North Atlantic basin over more than a year (Tesch 2003;Wang and Tzeng 2000;Miller et al 2015a). Larval catches or silver eel tagging studies indicate that in addition to A. rostrata, the eels of A. japonica, A.…”

Ecology of Anguilliform Leptocephali: Remarkable Transparent Fish Larvae of the Ocean Surface Layer

“…Spawning seasons of temperate anguillids have been roughly estimated from the timing of the downstream migrations of silver eels into the ocean (Jellyman 2003;Tesch 2003) Kleckner and McCleave 1988;Tsukamoto 1992;Tsukamoto et al 2003). The timing of spawning of tropical anguillids is much less understood, however, even though seasonal differences have been observed in the presence or size of leptocephali in the central Indonesian Seas (Wouthuyzen et al 2009) and off west Sumatra in the eastern Indian Ocean (Jespersen 1942;Aoyama et al 2007).…”

“…Temperate anguillid eels clearly have seasonal cycles of migration and offshore spawning that result in their leptocephali being abundant in the spawning areas and larval migration routes at certain times of year. Less is known about the spawning seasons of tropical anguillids that appear to spawn at various times of the year Kuroki et al 2006a), but may have seasonal cycles of downstream migration and spawning linked to tropical monsoon cycles (Wouthuyzen et al 2009). Similarly little is known about seasonal patterns of spawning of most marine eels, but some information is available in a few areas of the world where collections have been made at multiple times of year, such as off South Africa (Castle 1968), the Sargasso Sea McCleave 1994, 2007), Gulf of Mexico (Smith 1989a), Gulf of Guinea (Blache 1977), or at least during two times of the year near Japan Minagawa et al 2007) and in the Indonesian Seas (Miller et al ,c, 2004Wouthuyzen et al 2005).…”

An Evaluation of Major Nutrients of Four Farmed Freshwater Eel Species (Anguilla japonica, A. rostrata, A. bicolor pacifica and A. marmorata)

“…2014 (A. rostrata), (A. bicolor bicolor or bicolor pacifica A. marmorata) (A. mozambica) . (Daverat et al, 2006;Leander et al, 2012), (Wouthuyzen et al, 2009;Han et al, 2012), (Gagnaire et al, 2011), (Luo et al, 2013) , . A. rostrata, A. bicolor pacifica A. marmorata A. japonica .…”