Onshore-offshore distribution and abundance of tuna larvae (Pisces: Scombridae: Thunnini) in near-reef waters of the Coral Sea

The on-offshore distributions of tuna larvae in near-reefwaters of the Coral Sea, near Lizard Island (14°30ʹS, 145°27ʹE), Australia, were investigated during four cruisesfrom November 1984 to February 1985 to test the hypothesis that larvae of these oceanic fishes are found in highest abundance near coral reefs. Oblique bongo net tows were made in five on-offshore blocks in the Coral Sea, ranging from 0–18.5 km offshore of the outer reefs of the Great Barrier Reef, as well as inside the Great Barrier Reef Lagoon. The smallest individuals (<3.2 mm SL) of the genusThunnus could not be identified to species, and are referred to as Thunnus spp. We found species-specific distributional patterns. Thunnus spp. and T. alalunga (albacore) larvae were most abundant (up to 68 larvae/100 m2) in near-reef (0–5.5 km offshore) waters, whereas Katsuwonus pelamis (skipjack tuna) larvae increased in abundance in the offshore direction (up to 228 larvae/100 m2, 11.1–18.5 km offshore). Larvae of T. albacares (yellowfin tuna) and Euthynnus affinis (kawakawa) were relatively rare throughout the study region, and the patterns of their distributions were inconclusive. Fewlarvae of any tuna species were found in the lagoon. Size-frequency distributions revealed a greater proportion ofsmall larvae inshore compared to offshore for K. pelamis and T. albacares. The absence of significant differencesin size-frequency distributions for other species and during the other cruises was most likely due to the low numbers of larvae. Larval distributions probably resulted from a combination of patterns of spawning and vertical distribution, combined with wind-driven onshore advectionand downwelling on the seaward side of the outer reefs.

Bibliographic Details

Main Authors:	Fowler, Ashely M., Leis, Jeffrey M., Suthers, Iain M.
Format:	article biblioteca
Language:	English
Published:	2008
Subjects:	Biology, Ecology, Fisheries,
Online Access:	http://hdl.handle.net/1834/25471
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