C: Food Chemistry & Toxicology JFS C: Food Chemistry and Toxicology Quality of Alaskan Maricultured Oysters ( Crassostrea gigas): A One-Year Survey A.C.M. OLIVEIRA, B. HIMELBLOOM, C.A. CRAPO, C. V ORHOLT, Q. FONG, AND R. RALONDE ABSTRACT: The objective of this project was to provide relevant information to Alaska shellfish growers regarding the intrinsic quality of their farmed oysters. A 1-y study was conducted to determine the condition indices, proximate composition, fatty acid content, and microbial load of commercially harvested oysters from 3 different mariculture regions in the state of Alaska. Oysters from farms located in the regions of Prince William Sound, Kachemak Bay, and Southeast Alaska were sampled according to the farmers’ harvest schedules. Our results suggest that Alaskan maricultured oysters have slight seasonal and regional differences. The condition indices of Alaska oysters were high, indicating an excellent quality product. The chemical composition and fatty acid profile of C. gigas from Alaska waters are in agreement with the values reported for mariculture oysters of same species from different parts of the world. The microbial content of Alaskan oysters varied widely between shipments from each specific geographic region and could not be correlated to either harvest time or transit time. Keywords: Alaska, mariculture, Pacific oyster, shellfish Introduction D uring the early 1900s Pacific oysters (Crassostrea gigas) were introduced in the state of Alaska with seed imported from Japan. At that time, the oysters were grown in intertidal zones of beaches, which proved difficult due to high natural predation and harsh climate conditions (Yancey 1966). The oyster industry in the state of Alaska remained dormant until the 1970s with the intro- duction of the suspended culture method. This method involves placing oysters in lantern nets or cages that are hung from floats or rafts anchored to the sea floor in waters that are 10 m to 40 m deep (RaLonde 1992; Alaska Shellfish Growers Assn. 2005). Oysters remain submerged in water at all times, feeding continuously and independently of the changes in tides (Painter and RaLonde 1993). Since then, Alaskan oysters have been successfully grown in sus- pended culture systems until they reach market size (Painter and RaLonde 1993). In 1994 the 1st shellfish hatchery was established in the city of Seward, and oyster farming became a growing enterprise for Alaska’s coastal economy (Chew 2001). The driving force behind the interests and entries into shellfish farming in the state can be attributed to the increasing demand and trade of shellfish domes- tically and internationally (Pacific Aquaculture Caucus 2004). From 1990 to 2005, farmed Pacific oyster production in Alaska increased 6-fold to over 1.3 million oysters and $566,000, while farmers expe- rienced more than a 30% increase in price received for their oysters (Alaska Dept. of Fish and Game 2005). Alaska oysters differ considerably from oysters grown in warmer climate areas as spawning generally does not occur during their life cycle (Conte and others 1997). Gamete maturation and spawning are temperature-dependent biological processes. Prolonged tempera- tures above 10.5 ◦ C are needed to mature C. gigas gametes, while spawning is triggered with a temperature shock of 18 to 22 ◦ C (Mann MS 20060297 Submitted 5/24/2006, Accepted 9/13/2006. Authors Oliveira, Himelbloom, Crapo, Vorholt, and Fong are with Fishery Industrial Technol- ogy Center, Univ. of Alaska Fairbanks, Kodiak, AK 99615, U.S.A. Authors Crape, Fong, and RaLonde are with Marine Advisory Program, Univ. of Alaska Fairbanks, Anchorage, AK 99501, U.S.A. Direct inquiries to author Oliveira (E-mail: ffamo@uaf.edu). 1979; Quayle 1988). During the spawning season oysters are unsuit- able for consumption due to physiological changes that affect chem- ical composition, appearance, and taste of the product (Painter and RaLonde 1993; Conte and others 1997). Many farms exceed water temperatures of 12 ◦ C for only a short summer period, and this is not sufficient for significant gamete mass development. Applying wa- ter temperature data from Alaska farms into a model developed by Mann (1979) yielded results showing that Alaska oysters only reach about 50% to 70% of the temperature units required for matura- tion; thus shellfish growers in the state have the unique opportunity to provide a year-round supply of fresh product to restaurants and live shellfish markets. Another important characteristic of C. gigas is that higher environmental temperatures will lead to larger oysters; however, lower water temperatures favor higher absolute meat pro- duction and higher conditioning indices (Mann 1979). This char- acteristic of Alaska oysters was recently confirmed by Damar and others (2005). The researchers developed a method to predict oyster volume and weight with a machine vision system using maricultured Texas, Florida, and Alaska oysters. The highest ratios of meat-to-shell weight were recorded for Alaskan oysters, which showed an average condition index about 25% higher than either Texas or Florida oys- ters (Damar and others 2005). On the other hand, Alaska oysters are slower growers when compared to oysters grown in warm wa- ters, with harvest time ranging from a minimum of 1 y for small-size oysters to a maximum of 3 y for large-size oysters. Figure 1 depicts the 3 main regions in Alaska where oyster farms are located. In any of these regions, Prince William Sound, Kachemak Bay, and Southeast Alaska, most shellfish farms are found in remote geographic locations where farmers can take advantage of pristine water quality rich in nutrients (Harrington 2005). Little concern ex- ists regarding water pollution resulting from human or industrial activities and Alaska has no prohibited or restricted shellfish grow- ing areas (Alaska Shellfish Growers Assn. 2005). In contrast, due to the distance to market Alaska oyster producers are at great disadvan- tage when compared to shellfish producers in other states. Because raw oyster quality is highly dependent on transit time and temper- ature from grower to consumer, farmers in Alaska must make use of expensive jet transport to rush their refrigerated shellfish product C532 JOURNAL OF FOOD SCIENCE—Vol. 71, Nr. 9, 2006 C  2006 Institute of Food Technologists doi: 10.1111/j.1750-3841.2006.00186.x Further reproduction without permission is prohibited