The Effect of Seasons on Gill Net Selectivity

Abstract

In this study, the aim was to investigate the seasonal variations in the selectivity of striped red mullet (Mullus surmuletus L., 1758) captured by gill nets during the year in the north Aegean Sea. Fisheries’ operations were carried out between August 2008 and August 2009. Gill nets with 18, 20, and 22 mm mesh sizes were used in the trials. These nets are widely used in the region. Gill nets were deployed three hours before sunset and were removed from the sea at sunset. Similarly, the nets were set up two hours before sunrise and hauled from the sea an hour after sunrise. The SELECT method was used to determine the selectivity of gill nets. The deviances from the SELECT method revealed that lognormal models gave the best fits for all seasons. As a result of the calculations made according to the lognormal model, the modal lengths of the gill nets were calculated as the shortest in the spring season and the longest in the summer. The spread values of the selectivity curves of the experimental gill nets were determined the lowest in the winter season and the highest in the summer season. As a result of selectivity analysis, the differences between the spring and summer season modal lengths of the nets were calculated as 1.5 cm, 1.65 cm, and 1.82 cm for the nets with 18 mm, 20 mm, and 22 mm mesh sizes, respectively. The study results showed that the fishing season was important in gill nets selectivity.

Keywords

• Seasons,gill net,selectivity,SELECT method,Aegean Sea

References

1. Amin, A. M., Madkour, F. F., Abu El-Regal, M. A. & Moustafa, A.A. (2016). Reproductive biology of Mullus surmuletus (Linnaeus,1758) from the Egyptian Mediterranean Sea (Port Said). International Journal of Environmental Science and Engineering, 7, 1–10.
2. Arslan, M. & İşmen, A. (2013). Age, growth and reproduction of Mullus surmuletus (Linnaeus, 1758) in Saros Bay (Northern Aegean Sea). Journal of Black Sea/Mediterranean Environment, 19(2): 217–233. Clarke, J. R. (1960). Report on selectivity of fishing gear. InternationalCo mmission for the Northwest Atlantic Fisheries Special Publication, 2, 27–36.
3. Carol, J. & Garcia-Berthou, E. (2007). Gillnet selectivity and its relationship with body shape for eight freshwater fish species. Journal of Applied Ichthyology, 23, 654–660.
4. Hamley, J. M. (1975). Review of gillnet selectivity. Journal of the Fisheries Research Board of Canada, 32, 1943–1969.
5. İlhan, D. U., Akalın, S., Özaydın, O., Tosunoğlu, Z. & Gurbet, R. (2009). Growth and reproduction of striped red mullet (Mullus surmuletus L., 1758) in Izmir Bay (In Turkish). Ege Journal of Fisheries and Aquatic Sciences, 1, 01–05.
6. Kolding, J. & Skålevik, Å. (2011) PasGear 2. A database package for experimental or artisanal fishery data. Version 2.5. available at http://www.imr.no/forskning/utviklingssamarbeid/eaf_nansen_programmet/pasgear_2/en
7. Millar, R. B. (1992). Estimating the Size-Selectivity of Fishing Gear by Conditioning on the Total Catch. Journal of the American Statistical Association, 87, 962–968.
8. Millar, R. B. & Holst, R. (1997). Estimation of gillnet and hook selectivity using log-linear models. ICES Journal of Marine Science, 54, 471–477.

9. Millar, R. B. & Fryer, R. J. (1999). Estimating the size-selection curves of towed gears, traps, nets and hooks. Reviews in Fish Biology and Fisheries, 9, 89–116.
10. Moth-Poulsen, T. (2003). Seasonal variations in selectivity of plaice trammel nets. Fisheries Research, 61, 87–94.
11. Qeirrolo, D. & Flores, A. (2016). Seasonal variability of gillnet selectivity in Chilean hake Merluccius gayi gayi (Guichenot, 1848).
12. Pajuelo J. G. Lorenzo, J. M. Ramos A. G. & Méndez-Villamil, M. (1997). Biology of the red mullet Mullus surmuletus (Mullidae) off the Canary Islands, Central-East Atlantic. South African Journal of Marine Science, 18(1), 265–272.
13. Reis, E. G. & Pawson, M. G. (1999). Fish morphology and estimating selectivity by gillnets. Fisheries Research, 39, 263–273.
14. Torcu-Koç, H. Erdoğan, Z. Üstün, F. & Joksimovic, A. (2015). Some biological parameters of the striped red mullet (Mullus surmuletus L.) from the Bay of Edremit (Northern Aegean Sea, Turkey). Acta Adriatica, 56(2), 223–232.
15. Von Brandt, A. (1975). Enmeshing nets: gillnets and entangling nets - the theory of their efficiency. European Inland Fisheries Advisory Commission Technical Paper, 23(Supplement 1), 1, 96–116.