Consumer rating of the Suminoe oyster, Crassostrea ariakensis, during home cooking.

ABSTRACT The Suminoe oyster, Crassostrea ariakensis, is currently under consideration for introduction to the Chesapeake Bay for aquaculture and to restore lost fishery resources once provided by the native Eastern oyster. To assess the suitability of the Suminoe oyster for substitution into native oyster markets, we provided whole triploid oysters for home cooking to consumers in coastal North Carolina and asked them to complete a survey on qualities of the Suminoe oyster. Participants reported the frequency with which they would consume the oyster inside and outside of the existing oyster season, how they would consume the oyster and the price they might be prepared to pay for the Suminoe oyster relative to the native oyster. Because participants prepared the Suminoe oysters themselves, consumer evaluations incorporated not only attributes of the oyster meat but also the ease with which the oysters could be shucked and prepared. Consumers rated the Suminoe oyster's aroma, appearance, texture and flavor as likeable. As a result of the oyster's tissue quality and the ease with which it could be shucked, 81% indicated that they would purchase the Suminoe oyster if it is introduced. Only 19% of survey participants said they would pay more for Suminoe than Eastern oysters when both are available. This contrasts sharply with the 45% that would be prepared to pay a higher price for the Suminoe oyster than they would normally pay for Eastern oysters at times when the Eastern oyster is not available. Consumers generally indicated that they would prepare the non-native oyster in similar ways to the native oyster. Thus, our study indicates that the Suminoe oyster is considered by consumers in eastern North Carolina to be a close substitute for the native oyster. Consequently, the Suminoe oyster might serve as a successful substitute for the lost fishery resource of the native oyster.

KEY WORDS: oyster, Crassostrea ariakensis, consumer, fishery resource, market, non-native

INTRODUCTION

The decline of the native Eastern oyster, Crassostrea virginica (Gmelin 1971), along the midAtlantic coast of the USA has had profound environmental, social and economic consequences. Years of over-harvesting, habitat destruction, environmental degradation, diseases caused by the pathogens Perkinsus marinus and Haplosporidium nelsoni and poor resource management have led to a 99% reduction over the last century in oysters and the reefs they create (Rothschild et al. 1994, Frankenberg 1995). This change represents the loss of a "keystone species", one that shapes the entire estuarine system by controlling water quality (Newell 1988, Jackson et al. 2001), energy flow from the water column to the benthos (Ulanowicz & Tuttle 1992) and the production of fish and crustaceans (Peterson et al. 2003). The midAtlantic oyster fisheries, once the most prosperous in the USA, now fail to support even local demand for this resource, and oysters are imported into the region from the Gulf coast and Canada (Kirkley 1997, National Research Council (NRC) 2003).

In recent years there has been growing interest in the use of a non-native oyster to restore lost fishery resources once provided by the native Eastern oyster (Mann et al. 1991, Gottlieb & Schweighofer 1996, NRC 2003). Following in-water trials of non-native species (Calvo et al. 1999, Calvo et al. 2001, Grabowski et al. 2004), the Suminoe oyster, C. ariakensis (Fujita 1913), has emerged as a potential candidate for introduction to the midAtlantic either as a reproductive diploid for restoration of the wild fishery or sterile triploid for controlled aquaculture. It displays rapid rates of growth, survives at the low-medium salinities found throughout much of the Chesapeake Bay and Pamlico Sound, displays a high degree of resistance to P. marinus and H. nelsoni, and is palatable to local consumers (Calvo et al. 2001, Grabowski et al. 2003, Grabowski et al. 2004). Although there is growing support for a diploid and/or triploid introduction of the Suminoe oyster, implementation of either of these managerial strategies is contingent on substantial perceived economic, sociologic and ecologic benefits of the introduction out-weighing potential costs (NRC 2003).

Given that the major rationale of midAtlantic states for aggressive restoration of oyster reefs is usually the revitalization of the fishing economy (e.g., Kennedy & Breisch 1983, Hargis & Haven 1988), a key consideration in the introduction of a non-native oyster is its marketability relative to the native oyster. Surveys conducted in North Carolina in 2000 indicated that consumers preferred Eastern to Suminoe oysters when they were raw, but did not discriminate between the two species when they were steamed (Grabowski et al. 2003). In presenting consumers with pre-prepared oysters, these trials only considered attributes of the meat and the appearance of the oyster. Because oysters are consumed not only in restaurants but also in homes and at community events, the marketability of Suminoe oysters will, however, also be dependent on the ease with which oysters can be shucked and prepared.

Here we describe consumer perceptions of Suminoe oysters that participants were allowed to prepare for themselves in their desired traditional manner. Because the success of an oyster industry based on the Suminoe oyster may be dependent on its marketability at times when diploid Eastern oysters are not suitable for consumption, we compare consumer perceptions of Suminoe oysters between a period at the tail-end of the Eastern oyster season (April), when the native oyster is often gravid, and a period within the Eastern oyster season (November) when the quality of native oyster meat is generally high.

MATERIALS AND METHODS

We conducted our consumer evaluations of Suminoe oysters in the spring and fall of 2004. In each season, members of the North Carolina coastal community (predominantly from Hyde and Carteret counties) were provided with samples of 60-80 mm cultchless Suminoe oysters in shells that they shucked and prepared at their leisure using a method of their choice. Samples of oysters ranged in size from a peck to several bushels, Participants filled out a questionnaire as they consumed the oysters (Fig. 1) that asked them to rate the appearance, aroma, texture and flavor of the oysters on a scale of 1 to 10, where 1 is dislike extremely and 10 is like extremely. The questionnaire also required participants to describe how they prepared the oysters, how they think they would consume Suminoe oysters if they were commercially available, and whether they would be prepared to pay more for Suminoe oysters than Eastern oysters during and outside of the normal Eastern oyster season. So that the potential markets for Suminoe oysters could be compared with the existing Eastern oyster markets, participants provided information on when, where and how they consume Eastern oysters. Only surveys completed by traditional consumers of native oysters were considered. In spring, we received 82 valid surveys from participants representing a diverse range of ages (20-81 years old) and professions. In fall, the valid surveys numbered 128. Consumers were not simultaneously offered Eastern oysters because native oysters that had been cultured under similar conditions to the Suminoe oysters were not available.

Figure 1. Questionnaire supplied to participants.

ARIAKENSIS CONSUMER SURVEY

Please spend a minute completing this brief survey on the quality
attributes of Crassostrea ariakensis (Suminoe) oysters. Your
assistance will greatly assist us in determining the marketability
of these oysters.

DATE OF TASTING: --

Q1: How are you consuming the Crassostrea ariakensis oysters
    (please circle ONE):

    RAW / STEAMED / OTHER (PLEASE SPECIFY)

Q2: How often, on average, do you consume oysters during oyster
    season (please circle ONE):

    > WEEKLY / WEEKLY / BIWEEKLY / MONTHLY / LESS THAN MONTHLY / NEVER

Q3: How do you consume oysters (circle as many as apply)?

    RAW / STEAMED / FRIED / BROILED / STEWED / OTHER (PLEASE SPECIFY)

Q4: Where do you consume oysters (circle as many as apply)?

    AT HOME / AT COMMUNITY GATHERINGS / IN A RESTAURANT /
    OTHER (SPECIFY)

Q5: When you eat oysters either at home or in a restaurant, what
    quality attributes are most important to you?

    --

Q6: How does the appearance of the Crassostrea ariakensis appeal to
    you? Please circle ONE number from 1-10, where 1 = dislike greatly,
    5 = undecided and 10 = like greatly.

    Dislike Greatly   1 2 3 4 5 6 7 8 9 10   Like Greatly

Q7: What do you like/dislike about the appearance?

    --

Q8: How does the aroma of the Crassostrea ariakensis appeal to you?
    Please circle ONE number from 1-10, where 1 = dislike greatly,
    5 = undecided and 10 = like greatly.

    Dislike Greatly   1 2 3 4 5 6 7 8 9 10   Like Greatly

Q9: What do you like/dislike about the aroma?

    --

Q10: How does the texture of the Crassostrea ariakensis appeal
     to you? Please circle ONE number from 1-10,
     where 1 = dislike greatly, 5 = undecided and 10 = like greatly.

     Dislike Greatly   1 2 3 4 5 6 7 8 9 10   Like Greatly

Q11: What do you like/dislike about the texture?

     --

Q12: How does the flavor of the Crassostrea ariakensis appeal to you?
     Please circle ONE number from 1-10, where 1 = dislike greatly,
     5 = undecided and 10 = like greatly.

     Dislike Greatly   1 2 3 4 5 6 7 8 9 10   Like Greatly

Q13: What do you like/dislike about the flavor?

     --

Q14: What other attributes do you perceive in the samples?

     --

Q15: If Crassostrea ariakensis were reasonably priced, would you
     consume them in any of the following ways (circle as apply):

     RAW / STEAMED / FRIED / BROILED / STEWED / OTHER (PLEASE SPECIFY)

Q16: How often would you purchase Crassostrea ariakensis oysters during
     oyster season if they were similarly priced to Eastern oysters
     (please circle ONE)?

     > WEEKLY / WEEKLY / BIWEEKLY / MONTHLY / LESS THAN MONTHLY / NEVER

Q17: How often would you purchase Crassostrea ariakensis oysters
     OUTSIDE of the traditional oyster season if quality
     non-reproductive oysters were available at a reasonable price
     (please circle ONE)?

     > WEEKLY / WEEKLY / BIWEEKLY / MONTHLY / LESS THAN MONTHLY / NEVER

Q18: Would you be prepared to pay more for Crassostrea ariakensis
     oysters than eastern oysters at times when both are readily
     available?

     YES / NO

Q19: Would you be prepared to pay more for Crassostrea ariakensis
     oysters than you would usually pay for eastern oysters at times
     when eastern oysters are not available?

     YES / NO

All Suminoe oysters used in tastings were cultured in the Newport River, Carteret County, North Carolina in plastic mesh vexar cages, held on racks 15 cm above the surface of the sediment. The average salinity at this site was 30 ppt and the bottom, sandy-mud. The oysters, spawned at the Virginia Institute of Marine Sciences (VIMS) Aquaculture Genetics and Breeding Technology Center on July 2, 2003 were triploids resulting from crosses between first-generation diploid females from the west coast of the United States (Taylor Shellfish; Shelton, Washington) and first-generation tetraploid males (also from the West Coast). Between receipt of oysters on August 27, 2003 and deployment in final grow-out bags in the Newport River, oysters had been maintained at high density in 2-mm mesh bags at the Narrows, Swan Quarter. Oysters used in spring tastings remained in grow-out bags in the Newport River from February 6 to April 6, 2004. The fall-harvested oysters were grown out in the Newport River between May 28 and November 20, 2004.

Statistical Analyses

To compare consumers' perceptions of Suminoe oysters harvested in spring to those harvested in fall, we performed t-tests on consumer rankings of (1) appearance; (2) aroma; (3) texture and (4) flavor between these two seasons. F-tests done prior to these analyses indicated that in all cases the data satisfied the assumption of homogeneous variances. Differences in the proportion of respondents who would consider eating (1) Suminoe oysters and (2) Eastern oysters prepared using each of five common methods were assessed using [chi square] tests.

RESULTS

The results of our surveys indicate that consumers in eastern North Carolina are more likely to eat oysters at home than at other venues. Of all respondents, 87% consume oysters at home, 52% consume oysters at community gatherings and 62% consume oysters in a restaurant.

The participants of our study rated the appearance, aroma, texture and flavor of Suminoe oysters as likeable. Each attribute received an average score of >7 out of 10 (Fig. 2), where 1 is dislike greatly, 10 is like greatly and 5 is neither like nor dislike. Across all participants, there was no discrimination between the quality of oysters harvested in the spring, outside of the Eastern oyster season, and in the fall, within the Eastern oyster season (Fig. 2). Frequent consumers of oysters, however, favored the texture and flavor of oysters harvested in spring over those harvested in fall. We detected no seasonal difference in the rating of Suminoe oysters by infrequent consumers (Fig. 2).

[FIGURE 2 OMITTED]

Overall, respondents indicated that they would consume Sumihoe oysters less frequently than they currently consume Eastern oysters (Fig. 3). Nevertheless, 79% indicated that they would purchase Suminoe oysters within the Eastern oyster season and 81% indicated that they would purchase Suminoe oysters if they were available out of season. Although 66% of participants in our survey indicated that they consume oysters once a month or less, 20% of participants projected that their frequency of Suminoe oyster purchase would be greater than biweekly during the Eastern oyster season. Outside of the Eastern oyster season around 10% of participants would purchase Suminoe oysters at least biweekly. Of all respondents, 19% indicated that they would pay more for Suminoe than Eastern oysters when both are available. The proportion that would be prepared to pay a higher price for Suminoe oysters than they would normally pay for Eastern oysters outside of the existing Eastern oyster season was 45%.

[FIGURE 3 OMITTED]

Although respondents were not required to justify their responses to questions, a number of perceptions were frequently reported. Many participants commented favorably on the ease with which thin-shelled Suminoe oysters could be shucked, the oysters' high meat to shell ratio and the short cooking time of Suminoe oysters in their shells in the microwave. The thin shell, was, however, considered a disadvantage by several consumers who found that the oysters dried out rapidly and burned easily when roasted. The most frequently cited reason for not wanting to purchase the oyster was a philosophic objection to the introduction of a non-native species. Only 7% of consumers indicated a dislike for the flavor of the oyster by giving it a rating of <5 out of 10.

In general, consumers indicated that they would prepare Suminoe oysters in the same ways as they prepare Eastern oysters (Fig. 4). The proportion of respondents that would consume Suminoe oysters raw was, however, slightly smaller and the proportion that would consume Suminoe oysters fried, broiled or stewed slightly larger than the corresponding proportions that would consume Eastern oysters in these ways. Of these differences, only the tendency for greater consumption of broiled Suminoe oysters was statistically significant by a [chi square] test ([chi square] = 4.304, P = 0.038; Fig. 4).

[FIGURE 4 OMITTED]

DISCUSSION

The motivation for most deliberate introductions of molluscan species is economic gain. This incentive may be particularly strong when existing fisheries for analogous species are depleted (Mann 1979). Our study indicates that the Suminoe oyster, proposed for introduction to the Chesapeake Bay, is considered by consumers to be a close substitute for the native oyster such that if production costs are low, its introduction could prove an economic success.

Our study expanded on previous research examining consumer attitudes toward pre-prepared Suminoe oysters by allowing participants to prepare the oysters themselves, which is the most frequent way in which oysters are consumed by survey participants. In evaluating Suminoe oysters, consumers not only took into consideration attributes of the oyster meat but also the ease with which oysters could be prepared. Of the consumers surveyed, 81% indicated that they would purchase the Suminoe oyster if it becomes available. Many commented on the ease with which the oyster could be shucked. Consumers of triploid Suminoe oysters consistently rated the oyster's aroma, appearance, texture and flavor as favorable, regardless of whether the oyster was sampled within the existing oyster season (late fall to winter) or in late spring, when diploid Eastern oysters are not suitable for consumption. Although we accept that ratings may have been inflated because the oysters were provided to participants free of charge, the ratings nevertheless confirm that the Suminoe oyster is palatable to local consumers (Grabowski et al. 2003).

Results suggest that if introduced, the Suminoe oyster would not, at least initially, serve as a complete substitute for Eastern oysters. Participants in our survey indicated that they would not consume Suminoe oysters as frequently as they currently consume native oysters inside or outside of the existing oyster season, Compared with the 34% of respondents that currently consume Eastern oysters at least biweekly in season, only 19% indicated that they would consume Suminoe oysters this often. Around 20% of respondents indicated that they would never purchase Suminoe oysters--mostly because of a philosophic objection against the introduction of non-native species. Because many of these objectors indicated that they enjoyed the flavor of Suminoe oysters, the market for Suminoe oysters may, however, expand over time as these objectors become used to the idea of non-natives in the waterways. Overall, participants indicated that they would consume Suminoe oysters in similar ways as they currently consume Eastern oysters, although the proportion of participants that would consume broiled Suminoe oysters was slightly greater than the proportion that consume Eastern oysters cooked this way.

Our study, in combination with previous research on the Suminoe oyster (Grabowski et al. 2003), suggests that the non-native might be successfully marketed at a smaller size than Eastern oysters. Several participants in our consumer trials noted that the 60-80 mm Suminoe oysters were too large to be consumed on the half-shell and were best consumed cooked. Grabowski et al. (2003) reported meat weights of Suminoe oysters that were double those of Eastern oysters of similar length. By marketing the oyster at a smaller size, growers could reduce grow-out times and increase rates of turnover, producing aquaculture operations of greater profitability. In the case of a wild fishery based on the Suminoe oyster, however, reduction of the legal size of harvest would not necessarily be recommended because the harvest of oysters before they reach sexual maturity may reduce spawning stock biomass to an unsustainable level.

The results indicate that much of the economic value of a Suminoe oyster industry would be derived from triploidy of the oysters as opposed to species-specific traits. In contrast to diploid oysters that become gravid during the warmer months, triploid oysters maintain a high glycogen content year-round, Consequently, triploids often have a substantially longer marketable season (Allen & Downing 1986). Frequent consumers of Eastern oysters, who account for most east-coast oyster purchases, indicated that the texture and flavor of triploid Suminoe oysters were better in spring at a time when diploid Eastern oysters are often watery and unmarketable than in late fall, when the Eastern oyster is at its prime. Of the participants in our study, 45% indicated that they would be prepared to pay a higher price for Suminoe oysters than they would normally pay for Eastern oysters outside of the existing Eastern oyster season. This compares to only 19% who would pay more for Suminoe oysters when Eastern oysters are available. Triploid Eastern oyster aquaculture, however, can (and does in coastal North Carolina; J. and B. Schwartzenberg, pers. comm.) also serve this demand outside of season. Thus, it remains questionable whether the economic benefits of culturing triploid Suminoe oysters would extend beyond the benefits an aquaculture industry based on triploid Eastern oysters could provide, Additionally, because the cost of producing triploid oysters can be double that of diploids, a full economic analysis is required to properly assess the net value of a triploid market.

As with previous consumer surveys on Suminoe oysters (Grabowski et al. 2003), we considered only those opinions of local oyster consumers. Because of the health risks associated with the consumption of oysters, consumers like to know where oysters were obtained and people living in oyster-growing areas make up the bulk of oyster consumers (House et al. 2003). We acknowledge that information on consumer demand for the Suminoe oyster in higher-end markets such as the raw oyster bar is needed to supplement the results of this and previous consumer surveys in a full economic market assessment. In addition, information is needed on the suitability of the thin-shelled Suminoe oyster for commercial shucking and processing. Nevertheless, our study, which considered not only attributes of the Suminoe oyster's meat but also the ease with which the oyster could be shucked and prepared, indicates that consumers in eastern North Carolina view the Suminoe oyster as a close substitute for the native oyster. Consequently, the Suminoe oyster may serve as a successful substitute for the lost fishery resource of the native oyster.

ACKNOWLEDGMENTS

This research was funded by the North Carolina Division of Marine Fisheries, NOAA and the North Carolina Golden Leaf Foundation. J. Braddy, M. Ulery and D. Schmidt cultured the oysters and along with M. Marshall of the North Carolina Division of Marine Fisheries assisted with the distribution of samples and surveys. R. Graham and D. Newman organized oyster roasts in their respective counties, Carteret and Hyde, at which they distributed consumer surveys. Disease-free triploid seed was provided by S. Allen, Jr., of the Virginia Institute of Marine Sciences. J. Grabowski provided helpful comments on an earlier version of this manuscript.

LITERATURE CITED

Allen, S. K. & S. L. Downing. 1986. Performance of triploid Pacific oysters, Crassostrea gigas (Thunberg). 1. Survival, growth, glycogen content, and sexual maturation in yearlings. J. Exp. Mar. Biol. Ecol. 102: 197-208.

Calvo, G. W., M. W. Luckenbach, S. K. Allen & E. M. Burreson. 1999. Comparative field study of Crassostrea gigas (Thunberg, 1893) and Crassostrea virginica (Gmelin, 1791) in relation to salinity in Virginia. J. Shellfish Res. 18:465-473.

Calvo, G. W., M. W. Luckenbach, S. K. Allen & E. M. Burreson. 2001. A comparative field study of Crassostrea ariakensis (Fujita 1913) and Crassostrea virginica (Gmelin 1791) in relation to salinity in Virginia. J. Shellfish Res. 20:221-229.

Frankenberg, D. 1995. North Carolina Blue Ribbon Advisory Council on Oysters. Final report and recommendations. Raleigh, NC: NC DENR.

Gottlieb, S. J. & M. E. Schweighofer. 1996. Oysters and the Chesapeake Bay ecosystem: a case for exotic species introduction to improve environmental quality? Estuaries 19:639-650.

Grabowski, J. H., C. H. Peterson, S. P. Powers, D. Gaskill & H. C. Summerson. 2004. Growth and survivorship of non-native (Crassostrea gigas and Crassostrea ariakensis) vs. native (Crassostrea virginica) oysters. J. Shellfish Res. 23:781-794.

Grabowski, J. H., S. P. Powers, C. H. Peterson, M. J. Powers & D. P. Green. 2003. Consumer ratings of non-native (Crassostrea gigas and Crassostrea ariakensis) vs. native (Crassostrea virginica) oysters. J. Shellfish Res. 22:21-30.

Hargis, W. J., Jr. & D. S. Haven. 1988. The imperiled oyster industry of Virginia: a critical analysis with recommendations for restoration. Special report Number 290 in applied marine science and ocean engineering. Gloucester Point, VA: Virginia Institute of Marine Sciences.

House, L., T. R. Hanson & S. Sureshwaran. 2003. US consumers: examining the decision to consume oysters and the decision of how frequently to consume oysters. J. Shellfish Res. 22:51-59.

Jackson, J. B. C., M. X. Kirby, W. H. Berger, K. A. Bjorndal, L. W. Bots ford, B. J. Bourque, R. H. Bradbury, R. Cooke, J. Erlandson, J. A. Estes, T. P. Hughes, S. Kidwell, C.B. Lange, H. S. Lenihan, J. M. Pandolfi, C. H. Peterson, R. S. Steneck, M. J. Tegner & R. R. Warner. 2001. Historical overfishing and the recent collapse of coastal ecosystems. Science 293:629-638.

Kennedy, V. S. & L. L. Breisch. 1983. Sixteen decades of political management of the oyster fishery in Maryland's Chesapeake Bay. J. Env. Manag. 16:153-171.

Kirkley, J. 1997. Virginia's commercial fishing industry: its economic performance and contributions. Virginia Sea Grant Publication VSG-97-02. Gloucester Point, VA: Virginia Institute of Marine Sciences.

Mann, R. E. 1979. Exotic species in mariculture. Cambridge, Massachusetts: MIT Press. 363 pp.

Mann, R., E. M. Burreson & O. K. Baker. 1991. The decline of the Virginia oyster Fishery in the Chesapeake Bay: considerations for introduction of a non-endemic species, Crassostrea gigas (Thunberg, 1973). J. Shellfish Res. 10:379-388.

National Research Council (NRC). 2003. Study on non-native oysters in the Chesapeake Bay. Washington, DC: National Academies Press.

Newell, R. I. E. 1988. Ecological changes in Chesapeake Bay: are they the result of overharvesting the American oyster? In: M. P. Lynch & E. C. Krone, editors. Understanding the estuary: advances in Chesapeake Bay research. Baltimore, MD: Chesapeake Bay Research Consortium. pp. 536-546.

Peterson, C. H., J. H. Grabowski & S. P. Powers. 2003. Estimated enhancement of fish production resulting from restoring oyster reef habitat: quantitative valuation. Mar. Ecol. Prog. Ser. 264:249-264.

Rothschild, B. J., J. S. Ault, P. Goulletquer & M. Heral. 1994. Decline of the Chesapeake Bay oyster population: a century of habitat destruction and overfishing. Mar. Ecol. Prog. Ser. 111:29-39.

Ulanowicz, R. E. & J. Tuttle. 1992. The trophic consequences of oyster stock rehabilitation in Chesapeake Bay. Estuaries 15:298-306.

MELANIE J. BISHOP * AND CHARLES H. PETERSON

University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, North Carolina 28557

* Corresponding author. E-mail: [e-mail]