ADDRESSING OBSTICLES TO DEVELOPING OYSTER CULTURE IN HAWAIʻI

Abstract

A series of experiments was conducted on Oʻahu, Molokaʻi and Hawaiʻi Islands to examine specific factors that contribute to the feasibility of oyster culture for the state of Hawaiʻi. Two simultaneous studies were performed to measure the growth and condition index of five families of Crassostrea gigas (Pacific oyster) grown in the traditional Hawaiian fishponds of Heʻeia, Oʻahu, and Keawanui, Molokaʻi. Three of the oyster families (AA, AE, and EE) were produced by the Molluscan Broodstock Program (MBP) at Oregon State University. Two additional oyster varieties studied were the Midori strain of C. gigas, and a naturalized C. gigas strain found at Heʻeia fishpond called Oʻahu oysters. Oysters grew significantly faster in Keawanui than in Heʻeia fishpond (P = 0.004). There were significant differences in growth between the five families grown in Keawanui Fishpond (P = 0.035) but no significant difference was found between the same varieties grown at Heʻeia. Oysters grown in fishponds exhibited extremely high growth rates in excess of eight mm per month but suffered high mortality rates due to predation, biofouling and summer mortality. Midori oysters cultured in Hilo Bay, Hawaiʻi, had a significantly higher condition index than triploid or MBP oysters (P = 0.002). Regression analysis revealed that predation accounted for 57% of the variance in oyster mortality observed in Hilo Bay (P < 0.0001). Chlorophyll a was found to be a significant predictor for oyster growth, accounting for 40.8% of the variance in oyster growth in the Hilo Bay experiments (P < 0.0001). Analysis of various pest eradication treatments showed that the Super Salty Slush Puppy (SSSP) treatment adapted from Cox. et al. (2011) proved to be the most effective for removing the parasite Polydora websteri (oyster mudworm) from oysters without causing additional oyster mortality (P < 0.0001).