Red Bass

l_bohar_etpison Photo: Mandy Etpison

 

Lutjanus bohar  

Description and Distribution
The two-spotted red snapper, otherwise known as red bass, has a distribution inthe Indo-Pacific from east Africa to the Marquesas and Line islands, north to the Ryukyu Islands, and south to Australia.
Lutjanus bohar is a common commercial fish in some parts of its range; in other areas, however, it is known for being ciguatoxic (people are poisoned by consumption of ciguatoxic fish). Red bass has red with brownish black shading along its dorsal side. It has deep grooves that run from the eyes to the nostrils. They can live up to 56 years with maximum length reaching 90 cm (TL) (1,3,4,12).

Preferred Habitat
Red bass is more commonly found around oceanic islands than in continental areas. The species normally occurs at depths of 10 to 70 m, but can range from 4 to 180 m. The snapper inhabits coral reefs, including sheltered lagoons and outer reefs. It is usually found singly, often adjacent to steep outer reef slopes, but is occasionally found in groups at the base of reef slopes or drop-offs (1,3,4,14).

l_boha_range
The distribution map of L. bohar
Source: Redrawn from Fishbase 

Life History
L. bohar is a relatively long lived, slow growing and late maturing tropical fish. Female red bass matured at a much larger size at around 42.8 cm (FL) and older age (9.39 years) than males at around 30 cm (FL) (1.46 years). Females were reproductively active over many months, from August to April.

The species shows no evidence of hermaphroditism and does not undergo asynchronous oocyte development. Research shows that the snapper may migrate to deeper depths as they become older and larger. In shallow water, the ratio of males to females is about 1:1.3 while in deeper waters, the ratio becomes 1:2. The red bass feeds mainly on fishes, but also takes shrimps, crabs, amphipods, stomatopods, gastropods and urochordates (1,3,4,12,13,14,16).

Spawning Aggregations
L. bohar forms spawning aggregations regularly. Research indicates that the snapper aggregate to spawn every month in Papua New Guinea and the Solomon islands at during full moon and third lunar quarter. Spawning aggregations of the species involves several hundreds of fish aggregating near the surface of the sea (3,9).

Fisheries
L. bohar is commercially exploited and is also targeted as a gamefish with high market value.The snapper is mainly caught with handline, bottom longlines and bydemersal trawling. They can be found alive in food markets, as in Hong Kong, and are also utilized fresh and dried/salted. However, large fish from oceanic areas in the western Pacific are often ciguatoxic.
In some areas, such as the Seychelles, red bass is one of the main species caught by local fishers for consumption. In 2000, for instance, the annual catch of the snapper peaked at 127.5 tonnes, ranking fifth out of all reef fish harvested in that year (2875 tonnes). The catch of the species declined to about one-third in 2003, while total reef fish catches only declined slightly. Declines in L. bohar catches also occurred in Papua New Guinea. However, no significant decline can be observed in the Solomon Islands on the catch-per-unit-effort and numbers in spawning aggregations. In other areas the fish has a reputation for causing ciguatera poisoning and is not harvested for consumption. For instance, on the Great Barrier Reef (GBR), Australia, red bass have been avoided historically by most fishers because of their reputed toxicity and its capture has been prohibited on the GBR since 2003 because of its association with ciguatera poisoning. (5,6,7,9,10,11,12,15)

Mariculture
The species is being cultured at research level hatchery breeding; however, little commercial production is recorded. One mariculture record in found according to FAO data, that four tonnes of red bass is cultured in Taiwan in 2005 (Phillips M. 2009 pers comm. & 6).

Threats
Although the longevity, growth rate, natural mortality and slow sexual maturation would be expected to make L. bohar susceptible to over-exploitation, it has been postulated, through theoretical modelling and analysis of temporal trends in catch-at-age, that, in some cases, longer-lived populations may be better buffered against catastrophic events, such as periodic recruitment failure resulting from over-exploitation. This hypothesis is consistent with the "storage effect", which could negate certain predicted deleterious fishing impacts, particularly if older age groups predominantly reside in depths that are deeper than are usually fished and have effectively escaped from the fishery. These larger, older fish are likely to contribute the most towards recruitments. Further, larger, older red snappers are typically avoided by fishers in some areas due to concerns about ciguatera poisoning, which is known to be more likely to occur when larger fish are eaten. These factors, combined, may afford some degree of resistance to fishing impacts.
(3,4,8,9,12)

Conservation & Management
In general, the biological features of red bass suggest the need to adopt and adhere to precautionary management approaches. Given the increasing global demand for tropical reef fish, including snappers which are popular food species, fisheries managers have to revise their perceptions and assess the likely susceptibility of tropical snappers to over-exploitation.
L. bohar, is a species with moderate vulnerability to fishing. It might be protected by being included within various marine protected areas (MPA) in its geographic range. However, the effectiveness of protection in most cases of MPAs is not known and no specific conservation or management programme has been designed to manage exploited population of the species. The red bass has not been assessed for the IUCN Red List.
(2,3,5,7,8,13,15)

References

1. Allen, G.R. (1985) Snappers of the World. An Annotated and Illustrated Catalogue of Lutjanid Species known to Date. FAO Species Catalogue. Vol. 6. FAO. Rome. Pp. 208, Pl. I-XXVII.

2. Cheung, W.W.L., T.J. Pitcher and D. Pauly (2005) A fuzzy logic expert system to estimate intrinsic extinction vulnerabilities of marine fishes to fishing Biol. Conserv. 124:97-111.

3. Fishbase (2009) http://fishbase.mnhn.fr/Summary/SpeciesSummary.cfm?id=1417

4. Australian Museum (2009) http://australianmuseum.net.au/Red-Bass-Lutjanus-bohar-Forsskal-1775

5. FAO (1996) Precautionary approach to fisheries. Part 1: Guidelines on the precautionary approach to capture fisheries and species introductions. FAO Technical Paper No. 350. FAO, Rome.

6. FAOSTAT (2009) http://faostat.fao.org/site/629/default.aspx

7. Gillespie, C., Lewis, R.J., Pearn, J.H., Bourke, A.T.C., (1986) Ciguatera in Australia: occurrence, clinical features, pathophysiology and management. Med. J. Aust. 145: 584-590.

8. Galal N., R. F. G. Ormond and O. Hassan (2002) Effect of a network of no-take reserves in increasing catch per unit effort and stocks of exploited reef fish at Nabq, South Sinai, Egypt Mar. Freshwater Res., 53: 199-205

9. Hamilton R. (2003) A report on the current status of exploited reef fish aggregations in the Solomon Islands and Papua New Guinea - Choiseul, Ysabel, Bouganville and Manus Provinces, Western Pacific Fisher Survey Series: Society for the Conservation of Reef Fish Aggregations. Volume 1.

10. Hoffman A. & S. V. Hoffman (1978) An investigation into the utilization of the tropical red snapper (Lutjanus bohar)

11. Isbister, G.K. & M.C. Kiernan. (2005) Neurotoxic marine poisoning. The Lancet Neurology. 4(4): 219 - 228.

12. Marriott, R.J. & B.D. Mapstone (2006) Geographic influences on and the accuracy and precision of age estimates for the red bass, Lutjanus bohar (Forsskal 1775): A large tropical reef fish. Fisheries Research. 80 (2-3):322-328.

13. Marriott, R.J. & B.D. Mapstone, G.A. Begg (2007) Age-specific demographic parameters, and their implications for management of the red bass, Lutjanus bohar (Forsskal 1775): A large, long-lived reef fish

14. Talbot, F.H. (1960) Notes on the biology of the Lutjanidae (Pisces) of the east African coast with special reference to Lutjanus bohar (Forsskal). Ann. S. Afr. Mus. XLV 1, 549-579.

15. Sumaila, U.R., A.D. Marsden, R. Watson and D. Pauly (2007) A global ex-vessel fish price database: construction and applications J. Bioeconomics 9: 39-51.

16. Wright, A., Dalzell, P.J., Richards, A.H. (1986) Some aspects of the biology of the red bass, Lutjanus bohar (Forsskal), from the Tigak Islands, Papua New Guinea. J. Fish. Biol. 28: 533-544.