Orange roughy

Orange roughy
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Beryciformes
Family: Trachichthyidae
Genus: Hoplostethus
Species: H. atlanticus
Binomial name
Hoplostethus atlanticus
Collett, 1889

The orange roughy, red roughy, slimehead, or deep sea perch (Hoplostethus atlanticus) is a relatively large deep-sea fish belonging to the slimehead family (Trachichthyidae). The Marine Conservation Society has categorized orange roughy as "vulnerable to exploitation". It is found in 3 to 9 °C (37 to 48 °F), deep (bathypelagic, 180-to-1,800-metre (590 to 5,910 ft)) waters of the Western Pacific Ocean, eastern Atlantic Ocean (from Iceland to Morocco; and from Walvis Bay, Namibia, to off Durban, South Africa), Indo-Pacific (off New Zealand and Australia), and in the Eastern Pacific off Chile. The orange roughy is notable for its extraordinary lifespan, up to 149 years. It is important to commercial deep-trawl fisheries. The fish is actually a bright, brick-red color; however, the orange roughy fades to a yellowish orange after death.

Like other slimeheads, the orange roughy is slow-growing and late to mature, resulting in a very low resilience. They are extremely susceptible to overfishing because of this, and many stocks (especially those off New Zealand and Australia, which were first exploited in the late 1970s) have already crashed; recently discovered substitute stocks are rapidly dwindling. The flesh is firm with a mild flavour; it is sold skinned and filleted, fresh or frozen.[1]

Description

Fish in the Faroe Islands:
Orange roughy, Hoplostethus atlanticus
Faroese stamp issued: 7 Feb 1994
Artist: Astrid Andreasen

The orange roughy is not a vertically slender fish. Its rounded head is riddled with muciferous canals (part of the lateral line system), as is typical of slimeheads. The single dorsal fin contains four to six spines and 15 to 19 soft rays; the anal fin contains three spines and 10 to 12 soft rays. The 19 to 25 ventral scutes (modified scales) form a hard, bony median ridge between the pelvic fins and anus. The pectoral fins contain 15-18 soft rays each; the pelvic fins are thoracic and contain one spine and six soft rays; the caudal fin is forked. The interior of the mouth and gill cavity is a bluish black; the mouth itself is large and strongly oblique. The scales are ctenoid and adherent. The lateral line is uninterrupted, with 28 to 32 scales whose spinules or 'ctenii' largely obscure the lateral line's pores. The eyes are large.

The orange roughy is the largest known slimehead species at a maximum standard length (a measurement which excludes the tail fin) of 75 cm (30 in) and a maximum weight of 7 kg (15 lb). The average commercial catch size is commonly between 35 and 45 centimetres (14 and 18 in) in length. "Orange roughy" was renamed from the less gastronomically-appealing "slime head" through a US National Marine Fisheries Service program during the late 1970s, which identified (then) underused species that should be renamed to make them more marketable.[2]

Due to its longevity, the orange roughy accumulates large amounts of mercury in its tissues,[3] having a range of 0.30-0.86 ppm compared with an average mercury level of 0.086 ppm for other edible fish.[4] Based on average consumption and the recommendations of a National Marine Fisheries Service study, in 1976, the FDA set the maximum safe mercury level for fish at 1 ppm.[4] Regular consumption of orange roughy can have adverse effects on health.[5][6] Compared to most edible fish, orange roughy are a very poor source of omega-3 fatty acids, averaging less than 3.5 g/kg.

Life history

A preserved specimen on display at a museum

Orange roughy are generally sluggish and demersal; they form aggregations with a natural population density of up to 2.5 fish per m2, now reduced to about 1.0 per m2. These aggregations form in and around geologic structures, such as undersea canyons and seamounts, where water movement and mixing is high, ensuring dense prey concentrations. The aggregations are not necessarily for spawning or feeding; the fish are thought to cycle through metabolic phases (active or feeding and inactive or resting) and seek areas with ideal hydrologic conditions to congregate during each phase. They lose almost all pigmentation while inactive, when they are very approachable. Predators include large, deep-roving sharks, cutthroat eels, merluccid hakes, and snake mackerels.

When active, juveniles feed primarily on zooplankton such as mysid shrimp, euphausiids, mesopelagic and benthopelagic fish, amphipods, and other crustaceans; mature adults consume smaller fish, predominantly of the Chaetodontidae and Myctophidae families, and squid which make up to 20% of their diet. The diet of the orange roughy is depth-related, with adult diets inversely related to that of juveniles. For example, juvenile consumption of crustaceans is lowest at 900 metres (3,000 ft) but increases with depth while crustaceans in the adult diet peaks at 800–1,000 metres (2,600–3,300 ft) and decreases with depth. The consumption of fish is the opposite, juvenile consumption decreases with depth while adult consumption increases. This inverse feeding pattern may be an example of resource-partitioning to avoid intraspecific competition for the available food at depths where prey is less abundant. The orange roughy's metabolic phases are thought to be related to seasonal variations in prey concentrations. The inactive phase conserves energy during lean periods. Orange roughy can live up to 149 years.[7]

Reproduction

Orange roughy are oceanodromous, pelagic spawners: that is, they migrate several hundred kilometers between localized spawning and feeding areas each year and form large spawning aggregations (possibly segregated according to sex) wherein the fish release large, spherical eggs 2.25 mm (0.089 in) in diameter, made buoyant by an orange-red oil globule) and sperm en masse directly into the water. The fertilized eggs, which are said to be 2.0–2.5 millimetres (0.079–0.098 in), (and later larvae) are planktonic, rising to around 200 m (660 ft) to develop, with the young fish eventually descending to deeper waters as they mature. Orange roughy are also synchronous, shedding sperm and eggs at the same time. The time between fertilization and hatching is thought to be 10 to 20 days; fecundity is low, with each female producing only 22,000 eggs per kg of body weight which is less than 10% of the average for other species of fish. Also, spawning can last up to three weeks and starts around June or July. Orange roughy are very slow-growing and do not begin to breed until they are at least 20 years old, when they are around 30 cm (12 in) in length.[7]

The maturation age used in stock assessments ranges from 23–40 years,[8] which limits population growth/recovery, because each new generation takes so long to start spawning.

Lifespan

The maximum published age of 149 years was determined via radiometric dating of trace isotopes found in an orange roughy's otolith (ear bone).[9] Similarly, counting by the growth rings of orange roughy otoliths has given a maximum age of 125 to 156 years.[10] The validity of these results is questioned by commercial fishers as some state the former method is controversial and the latter method is known to underestimate age in older specimens. The issue has yet to be resolved definitively, but carries important implications relating to the orange roughy's conservation status.

Threats

Capture rate of orange roughy worldwide

In recent years, human consumption of orange roughy has risen drastically due to increased supply through new deep-sea trawling techniques. Its recovery rate from fishing is slow because its long lifecycle and sporadic reproduction make the fish prone to overfishing. Due to habitat damage of commercial trawling, some may not venture out during mating season.

The United States continues to import up to 8,620 tonnes (19 million lb) per year. Several major food retailers have established seafood sustainability policies dealing with orange roughy. Some, such as Giant Eagle, Kroger, and BI-LO/Winn-Dixie, allow the sale of the fish, while others, including Whole Foods, Safeway, and Trader Joe's, explicitly prohibit its sale.[11] A 2003 joint report by the TRAFFIC Oceania and World Wildlife Foundation Endangered Seas Program argues, "probably no such thing [exists] as an economically viable deep-water fishery that is also sustainable. Similarly, international agreements to reduce fishing capacity, to remove subsidies which encourage overfishing, to encourage co-operation in management of fish stocks and flag States to take responsibility for their vessels fishing on the high seas, appear to have gone largely unheeded, to the detriment of deep-sea species and their associated ecosystems."[8]

In addition to the dangers for the species, bottom trawling has been heavily criticized by environmentalists for its destructive nature. This, combined with heavy commercial demand, has focused criticism from both environmentalists and media.[12]

The Australian orange roughy fishery was not discovered until the 1970s, but by 2008, the biomass was down to 10% of the unfished level.[13] It was the first commercially sought fish to appear on Australia's endangered species list because of overfishing.[14]

Conservation

Conservation measures consist of enforced catch limits, and listings on various endangered species and do-not-eat lists maintained by governments and environmental activist organizations.

According to sustainable seafood guides, such as Seafood Watch (USA), the Royal Forest and Bird Protection Society of New Zealand,[15] the Marine Conservation Society (UK),[16] consumers should not consume this species.

Orange roughy is New Zealand's highest-value fishery, accounting for 17.2% of total finfish export earnings. The generally accepted fishery management practice is to quickly reduce the original biomass (fish-down stage) to a target of 30%. Once this target is achieved, quotas are set. For example, assuming a hypothetical unfished biomass of 100,000 tons, 70,000 tons are considered "surplus" and unrestrained fishing is allowed to remove it. Quotas are set to maintain the 30,000-ton target biomass. The catch size that allows this is the maximum sustainable yield and was originally believed to be 1,200 tons per year. By 2005, it became obvious this quota was too high.[17]

The New Zealand Ministry of Fisheries has reduced catch quotas each year because the species' maturation and reproduction rates have been repeatedly overestimated. Antons Trawling, Ltd. represents 66% of the orange roughy quotas, and appealed the northern fishery's (ORH1) 2008 quota, which reduced the total allowable catch (TAC) from 1,470 to 914 tons. In February 2008, the High Court overturned the new quota, ruling the Minister did not have the legal power to set quotas for ORH1 because the strict interpretation of the Fisheries Act required an accurate population assessment and comparison to how many there should be. Due to the expense and difficulty of conducting assessments, only 20% of the areas had assessments. The majority of the unassessed areas had TACs of 10 tons or less, with a few notable exceptions, such as ORH1. As assessments in these areas to replace existing monitoring systems were neither cost effective nor technically feasible, the court recommended amendments to the Act.[18][19]

However, the new quotas are estimated to sustainably support only 11% of the unfished population size. Also, catch misreporting is a serious and common problem, with one ORH1 permit holder pleading guilty in 2008 to exceeding his quota by 180 tons, which by itself represents 12% of the quota. Area limits and feature limits are also routinely exceeded. The Area A catch limit of 200 tons has been exceeded every year, while the 30-ton limit for the Mercury-Colville features had been exceeded in three of the four years preceding the study, including a catch of 64 tons in 2004-05. Since orange roughy is a valuable export, the Ministry of Fisheries has launched projects to study the fish.[20]

In 2010, Greenpeace International added orange roughy (deep sea perch) to its seafood red list, which contains fish generally sourced from unsustainable fisheries.[21]

See also

Notes

  1. ↑ "Science Fact Sheet: Orange Roughy, Delicacy from the deep". Archived from the original (– Scholar search) on July 9, 2007. Retrieved 2007-08-17.
  2. ↑ "Trade secrets: Renaming and mislabeling of seafood". Retrieved 2011-03-17.
  3. ↑ Updating the Existing Risk Management Strategy for Mercury in Retail Fish Health Canada
  4. 1 2 Mercury in Seafood Seafood Network Information Centre
  5. ↑ Techno-economic data on Mercury and major compounds INERIS June 13, 2006
  6. ↑ "Mercury: how much is safe?". Green Left. June 24, 1998. An average woman weighing 60 kilograms can ingest 60 x 0.1 = 6 micrograms of mercury per day without exceeding the EPA reference dose. If each gram of fish contains 0.2 micrograms of mercury, our average woman could only eat 6/0.2 = 30 grams of fish per day without exceeding the EPA reference dose.
  7. 1 2 Bulman, C.M.; Koslow, J.A. (June 4). "Diet and food consumption of a deep-sea fish, orange roughy Hoplostethus atlanticus (Pisces: Trachichthyidae), off southeastern Australia" (PDF). Marine Ecology Progress series (CSIRO Division of Fisheries) 82: 115–129. Retrieved January 16, 2013. Check date values in: |date= (help)
  8. 1 2 Managing risk and uncertainty in deep-sea fisheries: lessons from Orange Roughy
  9. ↑ Fenton, G.E; Short, S.A.; Ritz, D.A. (June 1991). "Age determination of orange roughy, Hoplostethus atlanticus (Pisces: Trachichthyidae) using 210 Pb: 226 Ra disequilibria". Marine Biology (Berlin/Heidelberg: Springer) 109 (2): 197–202. doi:10.1007/BF01319387. ISSN 0025-3162. Retrieved 2010-06-18.
  10. ↑ http://www.bbc.co.uk/nature/15991999
  11. ↑ "Carting Away the Oceans 7" (PDF). Greenpeace. May 2013. Retrieved 2013-06-06.
  12. ↑ "Case for trawl ban 'overwhelming'". BBC New. 2007-05-05. Retrieved 2006-11-15.
  13. ↑ Orange roughy: Down and out Australian Marine Conservation Society
  14. ↑ Darby, Andrew (2006-11-10). "Trawled fish on endangered list". The Sydney Morning Herald. Retrieved 2007-08-17.
  15. ↑ The Best Fish Guide 09-10
  16. ↑ Fish Online
  17. ↑ Industry Management Within the New Zealand Quota Management System: pdf.
  18. ↑ Orange roughy decision shows changes are needed Scoop February 26, 2008
  19. ↑ Proposed Amendment to the Fishery Act Office of the Minister of Fisheries
  20. ↑ http://www.unep.org/bpsp/Fisheries/Fisheries%20Case%20Study%20Summaries/Smith(Summary).pdf
  21. ↑ Greenpeace International Seafood Red list

References

Further reading

External links

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