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Larval ecology of Uku (Aprion virescens) in the Main Hawaiian Islands: a review from historical data
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2023
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Description:Aprion virescens (known in Hawaiʻi as uku, broadly, the green jobfish) are a commercially and recreationally important species in the main Hawaiian Islands (MHI). These eteline snappers are top predators on coral reefs throughout the Indo-Pacific and, although they are bottom fish like Hawaii’s Deep 7 species, they can be found in much shallower waters than other Deep-7 species. The current Essential Fish Habitat (EFH) designation for post-hatch (“larval”) uku extends from 0 to 240 m in depth and from island shorelines to the edge of the Exclusive Economic Zone (EEZ) of the United States. Uku employ a biphasic life cycle which includes a planktonic larval phase after hatch. However, little is known about this species' early life history, which is a critical part of the definition of EFH. We investigated the distribution of its abundance and oceanographic characteristics associated with larvae and pelagic juvenile uku observations. A comprehensive literature review and Indo-Pacific wide specimen inventory was combined with an examination of archived ichthyoplankton samples collected in the proximity of Oʻahu. Our final data set consisted of fewer than 300 records of individual larval uku collected throughout MHI from 1967 to 2012. We characterize size and habitat patterns for 230 larvae from preflexion (3 mm) to pelagic juveniles (30-mm total length) with associated environmental data (surface temperature, surface salinity, date of collection and collection depth). Larval observations from archived samples (2–6.5 mm total length) were restricted to the top 40 m of the water column and the majority of larvae were found 1–27 km from shore. Larvae from the literature (3–30 mm total length) were found 0.5–88 km from shore. We also evaluated sizes of settled benthic juveniles and discovered a knowledge gap; juvenile uku between 30 and 90 mm in length have yet to be recorded anywhere in the Pacific, and thus their habitat use during this critical settlement period is unknown. Our results extend existing information about larval uku habitat and highlight the need for more targeted studies on the early life stages, especially focused on pelagic larval duration (PLD), release depth and locations, of this commercially and culturally important species.
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Rights Information:CC0 Public Domain
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