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1 December 2012 Larval Competency of Red Abalone (Haliotis rufescens): A New Timeframe for Larval Distribution.
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Settling cues in the form of coralline algae were presented to groups of hatchery-reared red abalone (Haliotis rufescens, Swainson 1822) larvae daily from day 4 to day 32 posthatch (temperature, 14°C). Survival of postlarval abalone after settlement was monitored for 30 days to quantify the effect of delayed metamorphosis on the subsequent survival of benthic juvenile abalone. After exposure to live coralline algae, an average of 85% of the larvae metamorphosed and settled the following day. The number of settled postlarvae increased gradually the longer the settling cue was withheld. Postsettlement juveniles were raised in individual containers on mixed diatoms for up to 34 days. Red abalone larvae remained competent to settle 32 days after fertilization. Larvae that metamorphosed from day 4 through day 19 had longer survival during the next 30 days (average, 19%) than those presented with a settling cue from day 20 to day 32 (average, 8%). Statistical analysis using a threshold cut point indicated that the 20-day threshold marked a significant change in subsequent postlarval survival. A receiver—operating characteristic curve analysis indicated that the 20-day cut point predicted high or low future survival of postmetamorphic abalone 73.4% of the time. Larvae that swam for less than 20 days had postmetamorphic survival of 8 days or more, whereas survival was 7 days or less for postmetamorphic abalone that had swam previously for 20–32 days. A larval competency period of 20 days is significantly longer than the 5–7-day larval stage often used to estimate transport times for this species.

Thomas B. Mccormick, Lorraine M. Buckley, Gabriela Navas, Gloria Barber, Brianne Billups, Vanessa Gill, Brianna Jones, Nicholas Peterson, Brianna Saylor, and James Sayre "Larval Competency of Red Abalone (Haliotis rufescens): A New Timeframe for Larval Distribution.," Journal of Shellfish Research 31(4), 1183-1187, (1 December 2012).
Published: 1 December 2012

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