Elsevier

Fisheries Research

Volume 174, February 2016, Pages 298-308
Fisheries Research

Experimental test of optimal holding conditions for live transport of temperate sea cucumbers

https://doi.org/10.1016/j.fishres.2015.11.004Get rights and content

Highlights

  • Current transport conditions for sea cucumber and 5 low-cost variants were evaluated.

  • Markers of body wall condition and muscle integrity were compared among treatments.

  • Iced seawater yielded the best health conditions, survival rates, and meat quality.

  • Standard conditions yielded high mortality and low meat quality.

  • Findings will help stakeholders optimize the exploitation of temperate sea cucumbers.

Abstract

Sea cucumber is one of the top five luxury seafoods in Asia and its commercialization primarily revolves around the processed body wall. Hence, live transport and storage of sea cucumbers prior to processing must preserve the condition of the body wall and underlying muscles. Unlike most commercial shellfish on which industry standards are chiefly based, sea cucumbers lack a protective exoskeleton and have the ability to autolyze. Here, we tested the efficacy of different live storage methods on Cucumaria frondosa, a commercial species that is widely distributed in the North Atlantic and the Arctic. Current technologies and low-cost variants were experimentally tested under conditions prescribed for the transport of seafood in Canada. Markers of post-storage health, body wall condition and muscle integrity were compared among treatments. The most common method currently in use (icing and salting) yielded the highest rates of mortality and skin necrosis, whereas iced seawater emerged as the best storage condition. These findings should help stakeholders adapt their methodologies to optimize the exploitation of temperate and cold-water sea cucumber resources.

Introduction

Sea cucumbers have been consumed and used in traditional medicine for centuries in Asia; over the past 50 years they have become one of the most prized seafoods in the world (Fabinyi, 2012, Purcell, 2014, Yang et al., 2015). The most commonly traded product, known as beche-de-mer or trepang, consists of the sea cucumber body wall (skin), generally including the muscle bands, which is dried and sold as a luxury seafood (Purcell, 2014). In North America, muscle bands are sometimes fresh frozen and marketed separately (Hamel and Mercier, 2008a). Dried aquapharyngeal bulbs (labelled flowers), liquid or gel extracts and various supplements can also be found on the market. It is believed that the consumption of sea cucumber has significant health benefits (Bechtel et al., 2013, Cheung and Wu, 2012). Studies have shown that the body wall and muscles of sea cucumbers are important sources of high-value compounds exhibiting anticoagulant, anticancer, antioxidant and anti-inflammatory properties (Bordbar et al., 2011, Wen et al., 2010, Xia and Wang, 2015). Because body wall is the chief commercial product, special attention should be given to the storage and transport of live sea cucumbers following harvest in order to maintain their organoleptic and nutritional properties.

Compared to other shellfish, live sea cucumbers have proven difficult to store and transport, because they lack a protective exoskeleton and have the ability to autolyze when they are stressed or taken out of seawater (Duan et al., 2010, Zang et al., 2012). Autolysis is a physiological response which leads to dermis (body wall) degradation through protein breakdown (Wu et al., 2013). Endogenous proteases have been reported to be responsible for the autolysis process, which is often associated with changes in the organoleptic properties of the meat in various marine species (Sun et al., 2013). The formation of new compounds, following lipid oxidation and protein breakdown, alters the color, odour, flavour and texture of the meat (Ghaly et al., 2010, Rodríguez et al., 2009). During storage, transport, handling and processing, sea cucumbers are exposed to air and UV and undergo abrupt changes in temperature and salinity (Ji et al., 2008, Zhu et al., 2009). These factors may lead to damage of the body wall, promote the development of strong odour and even cause the animal’s death (Zhu et al., 2009). Furthermore, the digestive tract secretes enzymes (e.g., trypsin, chymotrypsin and cathepsin) which act in the hydrolysis of collagen (Yan et al., 2014), the main component of the body wall (∼70%). Dead or unhealthy sea cucumbers exhibit deteriorated body walls that decrease the final products’ quality and result in economic losses (Saito et al., 2002, Sun et al., 2013, Wu et al., 2013).

Market price for sea cucumber is based on many criteria that include general appearance (e.g., color, shape, texture) and smell (Kinch et al., 2008, Purcell, 2014, Tuwo, 2005), all of which can be affected by handling. Storage and transport methods of live marine organism have been investigated in fishes (Berka, 1986, Froese, 1998, Harmon, 2009), crustaceans (Barrento et al., 2012, Fotedar and Evans, 2011) and molluscs (Buzin et al., 2011, Wyatt et al., 2013). The few studies that have been conducted on sea cucumbers are restricted to the transport of hatchery-produced juveniles for restocking programs (Purcell et al., 2006, Zamora and Jeffs, 2014), and more generally apply to tropical species.

The shortage of data on storage and transport of live sea cucumbers for food processing, and on temperate or cold-water species in particular, may be explained by the chiefly artisanal nature of harvesting and processing techniques used in the Indo-Pacific countries, where harvests outside China have traditionally concentrated. Tropical sea cucumbers are generally handpicked, and immediately eviscerated, boiled and dried on the shore or a nearby site; processing is essentially manual (Hair et al., 2012, Purcell et al., 2013). In China, hatchery-produced juveniles of the temperate species Apostichopus japonicus are transported to the restocking sites either in damp sealed plastic bags without seawater or in buckets inside fiberglass tanks full of aerated seawater (Guo et al., 2014, Tan et al., 2014). Depending on the distance from the hatchery to the restocking site and the accessibility, transport can take more than 10 h (Tan et al., 2014).

In recent years, the overexploitation of high-valued sea cucumbers from Asia and the Indo-Pacific has led to the development of new fisheries for under-utilized species around the world (Anderson et al., 2011, So et al., 2010, Therkildsen and Petersen, 2006). The sea cucumber Cucumaria frondosa is the focus of an emerging fishery in the North Atlantic. This species is widely distributed in temperate and cold waters, occurring from the Arctic Ocean to Cape Cod as well as along the coasts of northern Europe and Russia (Hamel and Mercier, 2008a). The state of Maine (USA) was the first region to start a commercial fishery for C. frondosa in 1980, followed by several eastern Canadian provinces (Hamel and Mercier, 2008a, Rowe et al., 2009), as well as Iceland and Russia (Garcia et al., 2006, Gudimova et al., 2005, Hamel and Mercier, 2008b, Therkildsen and Petersen, 2006). Commercial harvest of C. frondosa was initially carried out with scallop gears; eventually, specific drag nets were designed to minimize bycatch and suit local conditions (Barrett et al., 2007). Storage of C. frondosa between the fishing wharfs and the processing plants can range from a few hours in Iceland to almost 2 days on the east coast of Canada (B. L. Gianasi, unpublished data).

With the expansion of sea cucumber fisheries in North and South America and northern Europe, and developing aquaculture ventures, the need to optimize storage and transport of cold-water and temperate species of sea cucumber from wharfs or farms to processing plants is increasing. Optimum storage conditions that minimize stress and mortalities are of significant value not only for the emerging industry around C. frondosa in the North Atlantic, but also for other commercially important temperate species around the world such as A. japonicus, Parastichopus californicus, C. japonica, and Australostichopus mollis.

The present study investigated the use of different media for refrigeration during live storage of the sea cucumber C. frondosa. Current methods used by the industry and low-cost variants were investigated, following the general guidelines of the fish inspection regulations of Canada (FIR, 2014). Individuals were classified according to health and body wall condition immediately after storage. Measurements of pH of the meat (body wall and muscle bands) were conducted and water quality in the storage tanks assessed. Finally, individuals were monitored post storage for survival and development of skin damage to identify the optimal storing method in order to obtain high-quality body wall and meat products.

Section snippets

Sea cucumber collection

Sea cucumbers weighing 8.1 ± 1.3 g (immersed weight) and measuring 12.2 ± 2.4 cm (contracted body length) were collected by divers in Bay Bulls, Newfoundland (47°17′44.6″N, 52°46′8.9″W), eastern Canada, at depths between 5 and 10 m. Dive collections were performed by the Field Services of the Department of Ocean Sciences with the required permits from the Department of Fisheries and Oceans Canada (DFO). Sea cucumbers were kept in holding tanks with running seawater at ambient temperature (1.2–2.1 °C)

Health condition of sea cucumbers in the storage tanks

Treatment 4 (iced seawater) resulted in the highest proportion of sea cucumbers (92 ± 4%) scored as exhibiting very good health (VG) after storage in the cold room for 48 h (Fig. 1A). No visible skin lesions could be observed in these individuals (Fig. 2A and B). They looked like freshly collected individuals, responding immediately to handling by contraction of the body and presenting a very faint fish smell. A single sea cucumber (8 ± 4%) in treatment 4 was scored lower (G), because of a small

Discussion

Live storage of sea cucumbers is a challenge due to their soft unprotected body wall and ability to autolyze when they are stressed or taken out of seawater (Duan et al., 2010, Zheng et al., 2012). Unlike fish and crustaceans, on which industry standards are largely based, sea cucumbers are not protected by any scales or hard exoskeleton that would prevent contact with ice, salt or any other media during storage. Deterioration of the body wall and underlying muscles, which together constitute

Conclusion

Taken together, the results of the present study indicate that storage in iced seawater generates the best overall health conditions, survival rates, and meat quality. This medium should therefore be favoured for transporting and storing the sea cucumbers before processing. While the method differs from the current industry standard used with C. frondosa along the eastern coast of Canada, the modification proposed should not involve any major financial cost. In the end, as the organoleptic

Acknowledgments

We thank Fogo Island Co-operative Society Ltd, especially Mr. Phil Barnes, for providing information and logistical support, and for supplying sea cucumbers for the experiments. We would also like to thank the staff of the Joe Brown Aquatic Research Building (JBARB) for technical assistance with the experimental setup, Matt Osse for helping with sampling and various measurements as well as an anonymous reviewer for their helpful comments on this manuscript. This study was supported by the

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