The Effect of Delayed Opening on Yield and Economy of Mullus barbatus Linnaeus 1758 and Upeneus pori Ben-Tuvia and Golani 1989 Fisheries in the Northeastern Mediterranean.
This study was carried out during the 2002-2003 fishing season (September 2002- April 2003) off the Karatas Coasts located at the entrance of the Iskenderun Bay. Sampling was conducted in monthly intervals through the stations chosen from 0-20 20-50 and 50-100m depth ranges. An evaluation for the fishing season was done by taking into account Mullus barbatus and Upeneus pori among the species which made up the main catch. At the end of this evaluation we found that if the beginning of the fishing season along the Northeastern Coasts of Turkey was delayed from September to October the increase in the TW of the stock of M. barbatus and U. pori would be
15.05% and 82.87% in turn; if it was delayed until November the above mentioned increases were calculated at the level of 82.87% and 83.36% respectively. From the commercial point of view by shifting the opening of the fishing season to November there would be a 350% increase in the income earned from the species M. barbatus. As a result we conclude that delaying the fishing season to November instead of September would be better for both the fish
stocks and the economy.
Key Words: Mullus barbatus Upeneus pori fishing season fisheries regulation.
According to Bilecenoglu et al. (2002) 390 fish species are known in the Mediterranean coasts of Turkey. The species variety of the region can easily be seen especially when considering that over 700 fish species are distributed throughout the whole Mediterranean Water System (Quignard and Tomasini 2000). The fishing activities in the Northeastern Mediterranean are generally characterized by coastal fishery that is operated by small boats. The demersal species with high economical values are mainly caught and landed by the bottom trawl fishing fleet (Dimech et al. 2008). Fishing is conducted in the Northeastern Mediterranean Coasts of Turkey between 20 to
150m depths (Bingel 1987).
It has been reported that the fishing activity in
1950s created a high fishing pressure on the regional fish stocks (AkyA1/4z 1957). Continuous contributions of new boats to the fishing fleet have also exposed the regional fish stocks to overfishing today (GA1/4cA1/4
and Bingel 1994a). As a result the fish stocks in the northeastern Mediterranean have been decreasing under the increased exploitation pressure. Considering both this fishing effort and the poor management of the fisheries of ideal stocks the situation is not sustainable (GA1/4cA1/4 and Bingel
1994a). There has been a decrease in the yield and catch per unit effort (CPUE) year by year (GA1/4cA1/4
2000). It has also been reported that a dramatic decrease in the average TL of the species is of economical importance as the species that have high
economical values are substituted by species that
have less economical value (GA1/4cA1/4 2000). In the study of GA1/4cA1/4 (2000) the series of stocks of CPUE in the Northeastern Mediterranean showed a yearly decrease in the demersal fish stocks such as Saurida undosquamis Mullus barbatus Upeneus moluccensis for 20 years (GA1/4cA1/4 2000).
GA1/4cA1/4 and Bingel (1994b) stated that the
highest yield by bottom trawl fleet along the Northeastern Mediterranean Coasts of Turkey should not exceed 7700 tones and fishing capacity should not exceed 20000HP. However the fishing capacity for Turkey's entire Northeastern Mediterranean was almost exceeded by the fishing boats based only in the Karatas Harbor (13500HP).
The studies carried out up to now point out
that the stocks of the Northeastern Mediterranean have been over-exploited and fishery is not sustainable (GA1/4cA1/4 and Bingel 1994b; GA1/4cA1/4 2000; Rochet et al. 2005). The limitation of the fishing effort (GA1/4cA1/4 and Bingel 1994b) or increases in mesh size are considered as solutions. However at present no technical measures or fishing effort regulations have been applied in the area. The presence of mixed fishery/multi-species fisheries type observed along the Northeastern Mediterranean means that enlarging the mesh size of the nets will not be an optimal solution to decrease the yields (Ozyurt 2003). Mediterranean Fisheries need to think of is the multispecies characteristics of their landings and how single species models may indicate that a fishery is non profitable due to overexploitation. Therefore some other measures such as Marine Protected Areas should be taken.
In this study we analyze the possibilities and positive effects of delaying the opening of the fishing season on fish stocks in the northeastern Mediterranean.
MATERIALS AND METHODS
This study was carried out between September 2002 and April 2003 by taking M. barbatus and U. pori samples from three stations (located at 0-20 20-50 and 50-100m depth) off Karatas Coasts located at the entrance of the Iskenderun Bay (Fig. 1). A commercial trawler was used for sampling (270 HP 19m overall length). A one hour haul as a unit was used throughout a period of eight months (day time) in the above-mentioned three stations. A traditional Mediterranean bottom trawl net type with cod-end mesh size 22mm (knot- to-knot) was used.
Samples were taken from each haul randomly (Holden and Raitt 1974) and preserved in 4% formaldehyde solution buffered by borax. In the laboratory the total length (TL) and total weight (TW) of each individual was measured to the nearest 0.1cm and 0.01g respectively. Trawl catch composition and the changes in the monthly CPUE (kg h-1) were determined.
The catch composition showed that M. barbatus and U. pori were the main species in catches and being in their fast growth period for new cohort it was decided to concentrate on both of these species.
The monthly mean TL TW CPUE value and percentage variation of mean TL and TW of M. barbatus are shown on Table I. The minimum mean TL was obtained in September (9.862.05cm); after this month this value shows an increase and reaches its highest level in April (13.431.94cm).
Mean individual weight of M. barbatus increases by 15.05% from September to October and by 58.95% between October and November (Table I). Taking this increase into consideration the obtained mean CPUE value as 15.57kg in September will become 17.91kg and 28.47kg respectively if the fishing season is delayed till October and November instead of September. In this case the CPUE value which was calculated as 3.11kg for the whole fishing season will become 4.73kg with increasing 52.58%. Besides this increase that will become as biomass it will lead to economic growth as well. In line with its commercial value M. barbatus is classified by fishermen into 5 different categories in terms of size that is extra 1st 2nd 3rd bizri=zibil barbun. While approximately the 60% of the total landing of September is bizri barbun (0.50TL kg-1 in the year 2002) the majority (60%) of the catch in November is 2nd barbun (1.75TL kg-1).
Therefore if M. barbatus is marketed in November instead of September the income earned from this species will increase by 350%. If this data is taken into consideration and the fishing season opens in November the fishermen will have a 290.22% increase in their incomes considering the 82.87% increase in the total biomass and the 350% increase in income.
Table I.- Monthly mean total length total weight CPUE value and % differences in length and weight of Mullus barbatus and Upeneus pori.
###Mean total length###Mean total weight###Increase in mean weight
###(cm)###(g)###compared to September (%)
As it is seen on Figure 2 throughout the studying period the 62.50% of the biomass of M. barbatus was gained in September 17.78% in October and the rest was caught in the other six months. This situation can be put forward as M. barbatus fishery is based on recruiting year-class. Moreover when the depth ranges are considered the biomass obtained from 0-20m depth range for
M. barbatus which is bound by a 3 mile prohibition is also destroyed with the opening of the fishing season. This data can be considered as an indicator that the fishermen have been in breach of the 3 miles prohibition. If the situation was not so no decrease would be expected in biomass obtained from 0-20m depth range.
The monthly mean TL TW CPUE value and
growth rate in length and weight of U. pori are given in Table I. The increase in the weights of individuals that belong to U. pori between September and October was calculated as 76.18% and between October and November as 4.08%. In the event that the opening of the fishing season is delayed till October instead of September the CPEU value will increase from 5.85kg to 9.75kg. With a longer delay to November it is obvious that this value will increase to 10.15kg. According to this result the calculated mean CPUE value obtained for the whole studying period as 1.58kg will increase up to 2.16kg an increase of 36%.
However since the U. pori is labeled together with the lowest price of M. barbatus there will not be any economic.
The relationship between time and growth in length was estimated as y=0.324x+8.806 (R2=0.648). One concludes from the Figure that the 43.75% of the total catch was caught in September and 23.80% was caught in October. In the event of the opening of the fishing season in October instead of September the CPEU value will increase from
5.85kg to 9.75kg increasing to 10.15kg with a longer delay to November. According to this result the calculated mean CPUE value obtained for the whole period as 1.58kg will increase to 2.16kg with a 36% increase. However since the U. pori is labeled together with the lowest price of M. barbatus there will not be any economic advantage.
Coral (1988) reported that M. barbatus is growing the fastest at age 1. Taking into account the fact that the reproduction period takes place in the period of May and September (increasing in July especially) for M. barbatus (Sahin et al. 1992 Sahin and Akbulut 1997) and when the fishing season starts in September individuals that belong to that year's cohort are exposed to a fishing pressure in their rapid growing period. Indeed Sahin et al. (1992) reported that in Southeastern Black Sea coast the majority (70%) of landed M. barbatus individuals consisted of young ones that are immature or maturing. The same finding is reported from Greek fisheries which have reported that Helenic demersal and inshore fisheries stocks are overfished (Stergiou et al. 1997; Stergiou and Petrakis 1993; Stergiou et al. 1994).
Also many important Helenic fish stocks including Mullidae family and hence commercial catches consist mainly of young fish (age 0+ to 2 years) (Stergiou et al. 1997; Petrakis et al. 1992; Stergiou et al. 1992).
First maturity length has been reported to vary from 10.0 to 13.5cm in previous studies for M. barbatus (Mert et al. 1983; Celik and Torcu 2000; Ismen and Ismen 2003; Ozyurt 2003). It is clearly seen that mean total length in September (Table I) is lower than the length at first maturity.
Considering the selectivity curves and the length at first maturity of M. barbatus (Mert et al. 1983; Celik and Torcu 2000; Ismen and Ismen 2003; Ozyurt 2003) and U. pori (Mert et al. 1983; Kaya et al. 1999) if the fishing season is to be opened in October or in November it is apparent that the negativities caused by the fisheries will be less.
Immature and smaller than the minimum
permitted landing size are caught on the opening of the fishing season in the eastern Mediterranean Coasts of Turkey and the same findings have been reported in Hellenic seas (Stergiou et al. 1997). Immature and small size catch are generally discarded or marketed illegally with low prices in both the Turkish and Hellenic markets (Stergiou et al. 1997).
In addition to this it is known that the primary production has reached to its maximum level in autumn season not only in whole Mediterranean (Zingano et al. 1995) but also in Northeastern Mediterranean (Kideys et al. 1989; Polat and Piner 2002). This situation offers an excellent growing opportunity for newly hatched M. barbatus individuals that are in a rapid growing period. Therefore opening of the fishing season should be delayed until November.
Another point is the price of fish at the beginning of the fishing season which is the lowest in comparison with other months. Both regional fish consumption behaviors and high weather temperature (average 26.1oC in September 21.6oC in October) have influence on the low price of fishes. Therefore the opening of fishing season should be delayed to cold months (average whether temperature in November 15.3oC) instead of September.
The data obtained from M. barbatus and previous studies indicated that fishing season must not be open before November. When all these data are evaluated and U. pori is considered it is obvious that the fishing season should not be opened before October.
As a result of the evaluation of the beginning of the fishing season if the fishing season in the area is to be opened in October instead of September biomass of M. barbatus that consists the
11.83% of the total catch can increase 82.82%. When the same positive affect is considered to happen in the other species it will increase the incomes of the fishermen and it will also be a rational decision about the fish stocks and make them more plentiful.
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|Author:||Cicek, Erdogan; Avsar, Dursun|
|Publication:||Pakistan Journal of Zoology|
|Date:||Aug 31, 2014|
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