importance to local
communities of fish
caught off the coast of
Qatar
J.H. Al-Jedah
M.Z. Ali and
R.K. Robinson
Hormuz (Ahmed, 1987), Qatar occupies a unique position and, from time immemorial, the people of Qatar, as well as those of the other Gulf States, have depended upon the sea as the main source of wealth. Indeed, until the 1940s, just before the discovery of oil and the subsequent increase in Qatari income, fishing and pearling were, respec-tively, the main sources of food and wealth in Qatar. Consequently, fish is one of the favourite meals in Qatar and the other countries around the Arabian Gulf, and large quantities of fish are caught for export or local consumption.
At the beginning of the twentieth century, the number of fishing boats was about 1,250 and the total number of fishermen was 12,000-14,000 ± somewhat equal to 50 per cent of the population of Qatar at that time. Fish production was estimated as 400-500 tonnes per annum (Ahmed, 1987). After the discovery of oil in Qatar, many fishermen deserted the sea for the petroleum industry, and there was a decrease in the number of fishermen to 600-800 only; the number of working fishing boats followed the same pattern and decreased to about 180. How-ever, developments in the technology of fishing, such as mechanisation of the fishing boats, the introduction of large boxes to preserve the fresh catch in ice during long journeys, and other modern fishing aids have helped to off-set this reduction and, as shown in Table I, catches landed in Qatar have doubled over the last ten years. Nevertheless, although the average consumption of fish in the Arab countries rose from 5.2kg/person/ year in 1985 to 6.4kg/person/year in 1993, there remains a serious shortfall of local availability compared to potential consump-tion (Musaiger and Miladi, 1996).
This rising demand is not unexpected for, while fish has always provided a welcome source of protein for coastal communities, attention has been focused recently on the relationship between fish consumption and a reduced incidence of cardiovascular diseases. This benefit has been attributed to the nature of the fat in fish and other edible marine organisms (Kotbet al.,1991), for fish oil, unlike fats from other foods, is the only type that supplies omega-3 polysaturated fatty acids, especially eicosapentaenoic acid (20:5 n-3) (EPA) and eicosahexaenoic acid
The authors
J.H. Al-Jedahis based at the Food Control Labratory, Doha, Qatar.
M.Z. Aliis based at the Faculty of Science, University of Qatar, Doha, Qatar.
R.K. Robinsonis based at the Department of Food Science and Technology, University of Reading, Reading, UK.
Keywords
Fish, Qatar, Nutrition
Abstract
This article focuses on the consumption of fish in Qatar and its health benefits for those living in the region. The nutritional value of fish from traditional fishing areas such as the UK has been much discussed but this article addresses the value of fish from warmer regions. Samples of popular fish were purchased from the local market in Qatar and were then analysed for levels of major nutrients and fatty acids. The likely nutritional impact of fish on the local diet was then evaluated. Problems of preservation of fresh fish, hygiene and mercury levels are also pointed out. Vigilance on behalf of the Public Health Authorities is urged to ensure the good reputation of fish in this region remains.
Nutrition & Food Science
Number 6 . November/December 1999 . pp. 288±294
(20:6 n-3) (DHA). It is claimed that the consumption of fish oils may help in the prevention and treatment of high blood pressure, asthma, arthritis, psoriasis and some cancers (Ward, 1995).
However, while the nutritional value of fish has been the subject of much discussion in traditional fishing areas like the British Isles, little has been published about fish from warmer regions. Consequently, the aim of this project was to:
. purchase samples of popular fish from the
local market in Doha; and
. analyse them for levels of major nutrients
and fatty acids, in order to evaluate the likely nutritional impact of fish on the local diet.
Materials and methods
According to the Department of Fisheries, around 12 species of fish are widely consumed in Qatar, and these are listed in Table II. On three separate occasions, specimens of each species that weighed at least 1kg were purchased from the local market as soon as possible after landing, and transported to the laboratory in a chill box part-filled with ice. On arrival at the laboratory, each specimen was gutted and filleted in the manner prac-tised in most homes, and the bone-free fillets were stored at 48C for a maximum of two hours before analysis.
Analysis of the fillets
One fillet, consisting of muscle tissue and a covering of skin on one side, was selected for
each species and macerated in a high-speed blender. Duplicate sub-samples were ex-tracted for determinations of moisture, crude protein, fat and ash; an indication of pH was obtained by direct insertion of a combined electrode into the macerate prior to removing the sub-samples. The pH meter was an Orion 720A.
The moisture content of each sub-sample was determined according to ADAS (1986), as was the ash content. The fat content was measured by extraction with petroleum spirit in a Soxhlet extractor (Kirk and Sawyer, 1991), and total nitrogen content of the sample was found by the Dumas method using a Leco Nitrogen Determinator (Leco Instruments Ltd, Stockport, UK); the protein content was calculated as total nitrogen multiplied by 6.25 (Kirk and Sawyer, 1991).
Analysis of fatty acids
For analysis of the fatty acids in the fat extracted from the sub-samples, methyl esters were prepared by saponification followed by acidification and finally methylation with diazomethane (Punstinenet al.,1985). The methyl esters were analysed by GC on a Shimidzu GC15A with C-R6A chromatopac integrator. A 3mm63M stainless steel 10 per cent Silar 10C column packed with 100-120 mesh Gas ChromQ was used. The injector and detector temperatures were maintained at 2508C. The column temperature was held at 1008C for 4 min, and then heated at a rate of 58C per min to a final temperature of 2108C and kept for 15 min. The total time of analysis
Table ILocal catches and imports of fresh fish into Qatar during 1987-1991; all figures in metric tonnes
Year Local Imports Total
1987 2677.9 464.5 3142.2
1988 3086.2 231.6 3317.8
1989 4374.0 309.9 4683.9
1990 5702.2 830.5 6532.7
1991 8136.2 717.8 8854.0
1992 7844.9 1104.1 4949.0
1993 6994.0 1278.0 8272.1
1994 5085.7 1030.9 6116.1
1995 4271.3 1227.3 5498.6
1996 4739.9 1121.1 5861.1
1997 5031.9 782.7 5814.7
Source:Department of Fisheries, Ministry of Agriculture and Municipalities (1997)
Table IIThe names of some of the species of fish that are commonly caught off the coast of Qatar
Local English Scientific
Jesh Yellow-spotted Cavalla Carangoids bajad
Shary Orange-spotted Emperor Lethrinus kalloptrus
Zubcidi Malabar Cavalla Carangoids malabaricus
Naisur Black-spotted Snapper Lutjanus fulviflamma
Karari Crevalle Alpes mate
Kofer Longspine Seabream Argyrops spinifer
Chanad Narrow-barred King Mackerel Scomberomorus commerson
Muttawa Painted Sweet-Lips Plectorhynchus pictus
Yanem Grey Sweet-Lips Plectorhynchus schotaf
Safi White-spotted Spinefoot Siganus canaliculatus
Hamour Greasy Grouper Epinephelus tauvina
Badah Whipfin Majarra Gerres filamentosus
Gargafan Goldline Seabream Rhabdosargus sarba
was 47 min. The fatty acids were identified by comparing retention times with corresponding standards obtained from Sigma Chemical Co., St Louis, USA.
Analysis of minerals
The ash was digested in 5ml of 2N HNO3
(Analar Grade) by boiling for about two minutes and then cooling to room tempera-ture. The cooled solution was filtered through Whatman filter paper (No. 41) and made up to 25ml with 2N nitric acid; a ``blank'' was prepared in a similar manner. The samples were then analysed for lead, iron, copper, zinc, calcium, magnesium and potassium by atomic absorption (AOAC, 1990).
Results and discussion
The chemical composition of fish comes quite close to that of land animals (Connell and Hardy, 1982), but there are a number of factors that affect the amounts of the major components. Nevertheless, fish can be classi-fied into three categories according to the content of fat, namely the low-fat category with 0.6-3.0 per cent fat, the medium-fat category with 3.5-7.0 per cent fat, and the high-fat category with levels that range from 8.1-15.3 per cent fat (Childs and King, 1993).
The fish caught in the Arabian Gulf and consumed fresh tend to fall into the low and medium-fat categories, although it should be noted that the data shown in Table III are from random catches and the fat contents
may vary between individual fish/groups of fish of the same species caught at different times or under different conditions
(Stanbsy, 1962). The season of the year plays a major role in determining fat content, which is at a maximum in the autumn and lowest in the winter (Eganet al., 1981). Moreover, the level of fat varies with reproductive status, the anatomical part from which the sample was taken and the type of flesh; light ``meat'' is leaner than dark ``meat'' (Thurston and Groninger, 1959; Childs and King, 1993).
The levels of individual fatty acids in fish will depend, of course, on the total fat content, and the percentage distribution of the fatty acids changes as the fat content of the fish rises and falls. When the fat content increases, the contribution of the monosatu-rated fatty acids increases from around 30 per cent to 50 per cent, while the level of polysaturated fatty acids decreases from 50 per cent to around 20 per cent (Childs and King, 1993). The fatty acid content of a fish may change also according to diet, but the fatty acid profiles of the common fish avail-able in the markets in Qatar (see Tavail-able IV) are probably fairly typical. As might be expected, the saturated fatty acids dominate the pattern, but essential fatty acids like eicosapentaenoic acid (20:5 n-3) (EPA) are present in all species.
The amount of protein in any given species of fish does not vary throughout the year in the same manner as the fat and water contents, and hence the values in Table III are probably a good indication of the average
Table IIIProximate composition of some common fish caught off Qatar (Gulf waters); all figures as g/100g of edible fillets and the average of three determinations
Species Moisture Fat Protein Ash pH
C. bajad 75.05 1.99 20.97 1.39 5.91
L. kalloptrus 77.01 0.35 21.02 1.47 6.10
C. malabaricus 74.60 2.25 20.33 2.33 6.03
L. fulviflamma 76.13 1.38 19.50 1.56 7.16
A. mate 73.64 2.66 21.47 1.35 5.78
A. spinifer 77.63 0.24 19.24 1.60 6.56
S. commerson 70.35 7.46 20.32 1.42 6.10
P. pictus 76.24 1.20 19.98 1.47 6.09
P. schotaf 73.40 4.93 18.69 1.40 7.23
S. canaliculatus 76.24 3.18 17.44 2.74 5.79
E. tauvina 77.67 0.75 18.64 1.90 6.13
G. filamentosus 74.24 2.15 20.86 1.38 6.61
protein contents of each species. It is relevant also that fish muscle, which consists mostly of white muscle, a small quantity of dark muscle and connective tissues, is more digestible than other animal proteins due to the lower level of connective tissue, and the quality of protein in fish compares favourably with the protein of other animals consumed as food.
In addition, it is well documented that fish is a better source of vitamins and minerals
than meat (Egan et al.,1981). The content
of vitamin B6(pyridoxine) in the flesh of high-fat fish is about the same as in beef, but the content of thiamine (B1) is very variable, especially in fresh water fish, due to the presence of thiaminase. Other B-group vitamins, e.g. riboflavin, are also repre-sented. The fat-soluble vitamins (A, D and E) tend to accumulate in high-fat species, but it is important that levels in the flesh of low-fat species may be low due to selective retention by certain organs, e.g. the liver. Fish is not an important source of vitamin C (Stansby, 1962), but it is a good source of
minerals, such as phosphorus, magnesium, iodine, iron, copper and most trace ele-ments. This point is confirmed by the data shown in Table V. The high levels of potassium could, in particular, be beneficial to consumers, as could the potential intakes of calcium and magnesium.
Preservation of fish
Given that the analysis of typical fish from the market in Qatar confirms their nutritional contribution to the diet and that fish is a popular meal, ensuring that fish reaches the consumer without spoilage becomes a major issue for countries with ambient temperatures above 258C. Obviously domestic refrigerators are now commonplace but, even so, many communities around the Gulf do not have access to appropriate storage for perishable foodstuffs.
Thus, fresh fish is a highly perishable product when compared to the carcasses of
Table IVFatty acid profiles of some popular fish caught off the coast of Qatar
Fatty acids
C16:0 24.5 20.3 27.9 29.0 23.6 24.7 24.2 27.9 27.1 42.0 26.5 27.1 27.5
C17:0 1.2 0.8 1.0 0.7 1.4 1.3 1.5 0.7 0.5 0.8 1.0 1.9 1.1
C18:0 10.7 9.4 9.8 10.1 10.0 10.9 8.6 10.3 6.6 6.3 10.5 8.2 12.2
C20:0 0.8 0.3 0.5 0.6 1.0 0.5 2.0 0.3 0.6 0.5 0.5 0.5 0.5
C22:0 0.3 - 0.3 0.2 0.4 - 0.4 0.4 0.4 0.6 0.4 - 0.3
SSaturates 41.6 32.3 42.2 44.8 41.3 40.8 45.1 45.2 39.4 56.9 43.2 41.9 45.6
C16:1 5.2 2.5 5.1 6.3 5.5 3.9 7.9 8.7 7.6 9.2 6.8 6.6 5.3
C17:1 1.3 1.2 1.0 1.5 1.2 1.4 1.5 1.8 1.5 0.7 1.8 1.3 1.6
C18:1 15.2 15.0 21.3 19.3 13.9 15.5 12.3 14.3 27.5 13.8 18.9 20.6 22.8
C20:1 0.7 - 0.4 0.3 1.0 0.2 1.9 0.3 0.4 0.4 0.1 0.1 0.3
SMonoenes 22.4 18.7 27.8 27.4 21.6 21.0 23.6 25.1 37.0 24.1 27.6 28.6 30.0
C18:2 1.2 1.6 1.0 1.4 1.6 1.1 2.3 0.9 1.6 2.0 1.6 1.6 1.4
S Polyenes 36.0 49.0 30.0 27.8 37.1 38.2 31.3 29.7 23.6 19.0 29.2 29.5 24.4
warm-blooded animals, because fish can offer spoilage micro-organisms a suitable environ-ment to survive in terms of high water activity, moderate pH (see Table III) and a good supply of nutrients. In addition, fishing methods may lead to heavy contamination. For example, fish caught by trawl net may have high counts of micro-organisms stirred-up from the bottom sediment, while the hygienic condition of some trawlers may be questionable also. Even storing fish in ice onboard may lead to heavy contamination, and many of these organisms could contribute to spoilage. In addition, it has been shown not only that bacteria and their metabolic pro-ducts are responsible for spoilage, but also that enzymes from fish tissues are involved (Shewan, 1972). Indeed, the presence of certain enzymes appears to be a prerequisite for optimal growth of bacteria, and a series of tissue enzyme reactions, immediately post mortem, appears to begin the process which eventually leads to spoilage (Hobbs, 1987). However, it is sometimes forgotten that the countries of the Middle East are surrounded by sea and/or criss-crossed by rivers, and that, hundreds of years ago, catching fish was the full-time job of the majority of the people in the region. Since modern methods of pre-servation were unknown, salting/drying and fermentation were the only ways to preserve the fish which was caught. Consequently, the drying of fish remains widespread in the Gulf region, and fish that are too small to market or strips of lean fish are often salted and dried in the sun. Many types of fermented fish product also arose in the Middle East
(Musaigeret al.,1990), and the principal forms are shown in Table VI.
The advantages of treating fish in this way is that fermentation offers a simple method with minimal expense for handling fish, even those of marginal quality, e.g. physically damaged during landing or small in weight like Sardinellasp. However, all these pro-ducts, including the popular fermented fish sauce, mehiawah, which is produced in the Arab Gulf States, are mostly made in the home by traditional methods, and their commercial potential has only recently be-come of interest. At present, one plant in Bahrain has begun production of mehiawah but, in spite of this development, control of the process is still imprecise, even though the reported shelf-life of the retail product is two years. Whether or not further developments can take place in this field remains to be seen but, as overfishing becomes a world-wide problem, so the prevention of waste will become a priority.
Marine environment and food safety
In general, warm-water fish seem to have a mesophilic, Gram-positive microflora (mi-crococci, bacilli, coryneforms), whereas cold-water fish harbour a predominantly Gram-negative, psychrophilic population, such as Moraxella, Pseudomonas, Flavobacterium, Aci-netobacter, Alteromonas, Cytophage and Vibrio (Shewan, 1972). More importantly, perhaps, caught fish are generally free from food poisoning organisms, and indeed of those organisms likeEnterococcus faecalisthat are
Table VMineral contents (mg/kg) of some common fish caught off Qatar (Gulf waters)
Species Iron Copper Zinc Calcium Magnesium Potassium
C. bajad 4.16 0.30 3.61 494.01 303.56 4683.90
L. kalloptrus 3.78 0.25 3.29 441.87 274.32 4958.04
C. malabaricus 4.68 0.75 3.29 328.52 282.68 4066.47
L. fulviflamma 5.66 0.85 4.89 826.54 269.98 3610.83
A. mate 10.89 1.69 5.18 357.00 252.54 4141.11
A. spinifer 6.30 0.74 3.46 566.95 296.06 4715.88
S. commerson 3.55 1.19 3.89 73.91 332.16 4976.03
P. pictus 3.58 0.74 2.41 524.63 269.01 4745.89
P. schotaf 5.74 0.96 4.19 570.10 285.71 3732.90
S. canaliculatus 6.87 1.11 6.14 206.09 315.97 3903.38
E. tauvina 3.24 0.66 3.70 284.32 275.20 4866.87
G. filamentosus 4.27 0.79 10.99 377.36 272.51 4433.64
used as indicators of faecal pollution. The only food poisoning bacteria found from fish caught away from areas of sewage pollution areClostridium botulinumandVibrio parahae-molyticus, so that contamination in fish with organisms of public health significance is essentially a problem of handling and processing that follows the catching (Hobbs, 1991).
As stressed before, the marine environment is an important source of human food for the people of the Gulf, where a deep culture of seafood consumption is reflected in the eating habits. Moreover, most of these countries use sea water, after distillation and purification, in drinking, cooking and washing, while the marine environment offers an additional benefit through aquaculture and fisheries resulting from the proliferation of planktonic algae (algal blooms). However, in some coastal regions, these algal blooms ± com-monly referred to as ``red tides'' ± can prove to be very harmful, and are responsible for many fatal cases of food poisoning due to the consumption of contaminated shellfish and planktivorous fish, such as sardine and anchovies (Hallegraeff, 1993). The discharge of waste from ships, oil tanks and industrial factories is another problem that could be harmful to marine life, as such wastes usually contain chemical contaminants, such as heavy metals and hydrocarbons. Mercury is a particular concern in the Gulf, with occa-sional samples of local fish having levels above the legal limit of 0.5mg/kg (Rao and Ahmed, 1995).
As a consequence, marine products of different kinds, such as fresh fish or the fermented products, could be affected by algal toxins and other marine contaminants,
and vigilance on the part of the Public Health Authorities will be necessary to ensure that the well-founded reputation enjoyed by fish in the Gulf region is not tarnished.
References
ADAS (1986),The Analysis of Agricultural Materials: A Manual of the Analytical Methods used by the Agricultural Development and Advisory Service, 3rd ed., Ministry of Agriculture, Fisheries and Food, London.
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Table VISome of the fermented fish products found in the Middle East
Name of food Species of fish Country Comments
Feseekh Mugil cephalus Egypt Usually eaten in public gardens during the festivities of Easter known as ``sham-al-naseem''
Terkin Tilapia sp. Sudan Fermented fish sauce, used in stew preparation
Salted sardines Sardinella sp. Gulf states Side dish
Mehiawah Sardinella gibosa Gulf states Fish sauce used for flavouring
Tareeh Sardinella spp. Gulf states Fermented fish paste, consumed with local bread
Katheef Mixed Gulf states Fermented whole fish
Awal Mixed Gulf states Dried, salted, fermented fish used in seasons of scarcity
Maleh Mixed Gulf states Fermented brined whole or halved fish, used in stews
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