Escolar and oilfish

Outbreaks of keriorrhea are reported in consumers who admitted having consumed various fishes (e.g., Atlanta cod, butterfish, cod, ruddercod, or rudderfish). However, so far, almost all episodes can be traced to two varieties escolar and oilfish. 

Escolar and oilfish belong to the Gempylidae (snake mackerel) family in the order Perciformes (Alexander et al., 2004 Nakamura and Parin, 1993). There are currently 24 species under 16 genera in Gempylidae, and they are all found in the marine environment (FishBase, 2008). All species in this family usually occur in very deep waters in tropical and subtropical seas (Nakamura and Parin, 1993). They have elongated and compressed body with isolated finlets after the anal and dorsal fins (Nakamura and Parin, 1993). 

FIGURE 1.2 (A) Escolar (Regulatory Fish Encyclopedia, U.S. FDA, 1993-2008, reprinted 

Atlantic and the other for the Pacific (plus four from South Africa) samples. A previous study by Collette et al. (1984), interestingly, also noted differences between escolar in the Atlantic and the Indo-Pacific regions, their vertebral counts being 31 and 32, respectively. There is a possibility that two species or subspecies of escolar may be warranted (Brendtro et al., 2008). 

Escolar and oilfish are commonly found at depths between 100-800 m and 200-1100 m, respectively (Nakamura and Parin, 1993). As in many 

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TABLE 1.1 Selected cases of keriorrhea outbreak related to escolar and oilfish consumption... 

Additionally, on the internet, there are discussions on the possibility of using escolar and oilfish for slimming or weight reduction. The value of this application is doubtful as only the oil (wax esters) would be discharged. 

As escolar and oilfish are widely distributed in the tropical and temperate seas, they are frequently caught and marketed as a result of by-catch with other commercially important species (Mori et al., 1966c Tserpes et al.,... 

Escolar and oilfish are of low commercial values because of their kerrior-rheic properties. They are considered as "not suitable for catering" or even banned from sale in various countries. However, they are commonly marketed as a result of their substantial by-catch with tuna and swordfish (Shadbolt et. ah, 2002 Tserpes et ah, 2006). According to the European Communities (Labelling of Fishery and Aquaculture Products) Regulations 2003 (S.I. No. 320 of 2003), L. flavobrunneum and R. pretiosus must be marketed as escolar and oilfish, respectively, and no other commercial names can be used alternatively. Yet, both species are usually mislabeled as sea bass, butterfish, rudderfish, white tuna, or codfish either... 

TABLE 1.2 Polices on escolar and oilfish in various countries or cities... 

Data from one escolar-associated outbreak found no correlation between BMI, age, health status, and amount of fish consumed to the severity and occurrence of symptoms, while other factors, such as variability in wax ester content in different fillet cut depths, could be relevant (Yohannes et al., 2002). Unlike some fish species, such as herring, which have uniform muscle oil content along the body (Brandes and Dietrich, 1953), muscle oil content in escolar and oilfish is not evenly distributed. Bone (1972) found that muscle oil content in oilfish increases from 14.5% (near vertebral column) to 24.7% (near the skin). A similar trend was also observed by Ruiz-Gutierrez et al. (1997) with higher oil content found in subcutaneous muscles than the periosteum. However, the lipid profile for... 

Polyacrylamide gel electrophoresis (PAGE) and cellulose acetate membrane electrophoresis (CAME) were applied to distinguish escolar and oilfish from 27 commercial fish based on muscle protein differences (Ochiai et al., 1984). Myogen fractions from the muscles were subjected... 

Escolar and oilfish contain a mixture of wax esters with different carbon-chain length, mainly C32, C34, C36, and C38, formed by combining different fatty acids and fatty alcohols. The dominant fatty acids in escolar and oilfish wax esters are the monounsaturated fatty acids (Table 1.3), namely oleic acid (18 1 oo9) and eicosenoic acid (20 loo9), while the dominant fatty alcohols are saturated and monoenoic fatty alcohols (Table 1.4), known as cetyl alcohol (16 0) and oleyl alcohol (18 1 9). PUFA, which are trace components in muscle wax esters, are commonly found in wax esters from roe, they include 20 4o)6, 20 5(b3, 22 5cd3 and 22 6 3. These differences could be due to the functional role in muscle for providing buoyancy, while that of roe is to store energy and key essential PUFA for fry development (Lee and Patton, 1989). 

TABLE 1.3 The major fatty acids in the wax esters of escolar and oilfish muscle... 

Indeed, fish roes, such as mullet roes, has long been consumed (Bledson et ah, 2003 Kalogeropoulos et al., 2008) and the roes from escolar and oilfish are advertised as high-priced souvenirs from Tungkang, Taiwan (Fig. 1.4). However, the high level of wax esters in these fish roes may cause keriorrhea if too much is consumed. 

Chua, L. H. (2007). "Potential Health Issues Associated with Consumption of Escolar and Oilfish." Agri-Food and Veterinary Authority, Singapore. http //www.ava.gov.sg/NR/rdonlyres/ 191531A0-5689-4DD9-9648-AE283FD78656/14747/Cir FoodTradersEscolarFishl.pdf. Accessed Nov. 5,2008. 

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