the-activity-of-collecting-sea-urchins-by-local-people-on-the-suli-beach-central-maluku

REASON TO KEEP THE SEA-URCHIN STOCK IN THEIR HABITATS

Written by

Wahyu Purbiantoro

Research Center for Deep Sea – Indonesian Institute of Sciences (LIPI)

 

Sea-urchins belong to the phylum Echinodermata. They are widespread throughout the world’s oceans, warm and cold. Humans have known to consume sea-urchin gonads since prehistoric era (Lawrence, 2007). The gonad is considered delicacies and is mostly consumed in the Mediterranean, and the Western Pacific. Today as fishery products, the sea-urchin gonads have become an important commodity in various countries, such as the United States, Japan, Chile, Spain, and France (Keesing & Hall, 1998). Then, the current market demand for sea-urchin products tends to increase, and it is predicted to grow in the future. Unfortunately, after reaching peak production in 1995, landings of wild sea-urchins continued to decline due to overfishing and lack of proper fisheries management (Andrew et al., 2002). However, the world production of sea-urchins essentially comes from the wild, and this activity looks ecologically unsound. Therefore, the unsustainable fishing of wild sea-urchins should be stopped because it can disrupt the balance of marine ecosystems, it reduces the economic potential of fisheries, and it can be managed with right fishing rules and replaced with aquaculture practice. 

First, over-exploitation of sea-urchins should be banned because it causes ecological damage. Sea-urchins are an important biological agent, and they are responsible for maintaining the health of coral reefs (Westbrook, Ringgang, Cantero et al., 2015). The depletion of sea-urchins leads to the growth of algae uncontrolled which covers the coral surface, thus inhibiting the formation of a new coral polyp and limiting total coral growth (Upham, 2015). In addition, sea-urchins provide a significant contribution to nitrogen cycles in seagrass ecosystems. Sea-urchins eat seagrass leaves in large quantities, but they have a limitation of absorbing nitrogen, so they excrete nitrogen in the form of ammonium in a significant amount. Afterwards, the bacteria will turn ammonium into nitrate which will be reused by seagrass (Koike, Mukai, Nojima, 1986). Moreover, sea-urchins are an important food source for other marine animals that live in the seagrass and reef ecosystems (Pearse, 2006). Some predators, such as triggerfish, starfish, wolf eels, sharks hunt and feed on sea-urchin gonads which are used as a protein source to meet their energy adequacy.

Another reason why overfishing of sea-urchins needs to stop is that it may reduce coastal community revenues from the fisheries sector. One of the ecological effects of the depletion of sea-urchins is to decline the health of coral reefs. Such losses often have a domino effect, not only on the coral reef ecosystems themselves but also on the local economies that rely on it. For example, fishermen will spend a lot to buy fuel because they are sailing farther than before. They have no choice because the amount of fish in shallow waters has diminished. Another example is the decline in incomes of local people who rely their lives on collecting ornamental fish. The reduced population of sea-urchins caused some species of ornamental fish to lose shelter. One of them is the Banggai cardinalfish which is a popular fish for aquarium display hiding among the spines of sea-urchins for protection against predators (Burton & Burton, 2017).

Finally, fishing of wild sea-urchins can be managed by arranging harvest time which is based on the maturity level of the gonads. According to previous research, spawning season generally occurs from October to December (Vaïtilingon, Rasolofonirina & Jangoux, 2005; Unuma & Walker, 2009). Therefore, fishing should be done from June to September, and it must leave some of the existing population. Another way that can be done to maintain the sea-urchin stock is cultivated commercial sea-urchin. Several articles have reported that some countries have successfully developed aquaculture system of sea-urchins, land base or offshore system (Agatsuma, Sakai & Tajima, 2010; Barker, 2010; Hagen & Siikavuopio, 2010; Kelly & Chamberlain, 2010; Liu, Zhu & Kelly, 2010; Pearce & Robinson, 2010).

In conclusion, there is no reason to continue excessive fishing of wild sea urchins. Some evidence has shown the damaging effects of marine ecosystems especially coral reef ecosystems due to depletion of sea urchin stock. The effects are not only on the coral reef communities themselves, but also on the coastal society income. Therefore, the regulation of fishing time and cultivation technology that has been developed must be supported to keep the sea urchin stock in their natural habitat.

References

Andrew, N.L., Agatsuma, Y., Ballesteros, E., Bazhin, A.G., Creaser, E.P., Barnes, D.K.A., Botsford, L.W., Bradbury, A., Campbell, A., Dixon, J.D., Einarsson, S., Gerring, P.K., Hebert, K., Hunter, M., Hur, S.B., Johnson, C.R., Juinio-Meñez, M.A., Kalvass, P., Miller, R.J., Moreno, C.A., Palleiro, J.S., Rivas, D., Robinson, S.M.C., Schroeter, S.C., Steneck, R.S., Vadas, R.L., Woodby, D.A., & Xiaoqi, Z. (2002). Status and management of world sea urchin fisheries. Oceanogr. Mar. Biol. Annu. Rev., 40, 343-425.

Agatsuma, Y., Sakai, Y., & Tajima, K. (2010). Recent advances in sea-urchin aquaculture in Japan. Bull. Aquacul. Assoc. Can., 108(1), 4-9.

Barker, M.F. (2010). Recent advances in sea-urchin aquaculture in New Zealand and Australia. Bull. Aquacul. Assoc. Can., 108(1), 10-17.

Burton, D., & Burton, M. (2007). Special adaptations. In D. Burton & M. Burton (Eds.), Essential Fish Biology: Diversity, structure and function (pp. 264-282). New York, the United States of America: Oxford University Press.

Hagen, N.T., & Siikavuopio, S.I. (2010). Recent advances in sea-urchin aquaculture in Norway. Bull. Aquacul. Assoc. Can., 108(1), 18-22.

Keesing, J.K., & Hall, K.C. (1998). Review of harvests and status of world sea urchin fisheries points to opportunities for aquaculture. J. Shellfish Res., 17, 1597-1604.

Kelly, M.S., & Chamberlain, J. (2010). Recent advances in sea-urchin aquaculture and enhancement in Scotland and Ireland. Bull. Aquacul. Assoc. Can., 108(1), 23-29.

Koike, I., Mukai, H., & Nojima, S. (1987). The role of the sea urchin, Tripneuates gratilla (Linnaeus), in decomposition and nutrient cycling in a tropical seagrass bed. Ecol. Res., 2(1), 19-29.

Lawrence, J.M. (2007). Edible sea urchins: use and life-history strategies. In J.M. Lawrence (Eds.), Edible Sea Urchin: Biology and Ecology (2nd ed., pp. 1-9). Oxford: Elsevier.

Liu, H., Zhu, J.K., & Kelly, M.S. (2010). Recent advances in sea-urchin aquaculture and enhancement in China. Bull. Aquacul. Assoc. Can., 108(1), 30-37.

Pearce, C.M., & Robinson, S.M.C. (2010). Recent advances in sea-urchin aquaculture and enhancement in Canada. Bull. Aquacul. Assoc. Can., 108(1), 38-48.

Pearse, J.S. (2006). Ecological role of purple sea urchins. Science, 314 (5801), 940-941.

Unuma, T., & Walker, C.W. (2009). Relationship between gametogenesis and food quality in sea urchin gonads. In R. Stickney, R. Iwamoto, & M. Rust (Ed.), Aquaculture Technologies for Invertebrates, Proceedings of the 36th U.S.-Japan Aquaculture Panel Symposium (pp. 45-54), New Hampshire & Connecticut, the United States of America.

Upham, V. (n.d). The importance of sea urchins. https://oceanbites.org/the-importance-of-sea-urchins/

Vaïtilingon, D., Rasolofonirina, R., & Jangoux, M. (2005). Reproductive cycle of edible echinoderms from the Southwestern Indian Ocean. I. Tripneustes gratilla L (Echinoidea, Echinodermatata). Western Indian Ocean J. Mar. Sci., 4(1), 47-60.

Westbrook, C. E., Ringgang, R.R., & Cantero, S.M.A. (2015). Survivorship and feeding preferences among size classes of outplanted sea urchins, Tripneustes gratilla, and possible use a biocontrol for invasive alien algae. PeerJ. doi: 10.7717/peerj.1235

 

an-interesting-association-between-fish-and-sea-urchins-astrophyga-radiata-in-the-ambon-bay_photo-by-soamole-a_1

an-interesting-association-between-fish-and-sea-urchins-astrophyga-radiata-in-the-ambon-bay_photo-by-soamole-a_2

Image 1 and 2. An interesting association between fish and sea urchins (Astrophyga radiata) in the Ambon bay_Photo by A. Soamole

fish-hide-among-the-spines-of-sea-urchins-diadema-setosum-for-protection-against-predators-in-the-ambon-bay_photo-by-purbiantoro-w

Image 3. Fish hide among the spines of sea-urchins (Diadema setosum) for protection against predators in the Ambon bay_Photo by W. Purbiantoro

the-activity-of-collecting-sea-urchins-by-local-people-on-the-suli-beach-central-maluku

Image 4. The activity of collecting sea-urchins by local people on the Suli beach, Central Maluku_Photo by W. Purbiantoro

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