Tevfik Ceyhan

Determination of Lmax for Atlantic Bluefin Tuna, Thunnus thynnus (L.), from Meta-Analysis of Published and Available Biometric Data

A meta-analysis of the straight fork lengths (herewith abbreviated as L) of 2,458,028 Atlantic bluefin tuna, Thunnus thynnus (L.), taken from 224 scientific publications and unpublished L data from scientific organizations and fishing companies spanning most of the known Atlantic and Mediterranean Atlantic bluefin tuna fisheries dating from 1605 to 2011, give L values ranging from L min = 20 cm and L max = 330 cm. The results indicate that the parameter L ∞ = 318.85 cm of the growth equation used by ICCATs Standing Committee on Research and Statistics Atlantic bluefin tuna assessment group for the eastern stock (Lt = 318.85 [1 – e−0.093 (t + 0.97)]) lies within the confidence limits of the maximum Ls presented in the study: L max = 319.93 ± 11.3 cm, confirming that this equation perfectly fits the biology of the growth of this species. These conclusions are also valid for the equation for the western stock (Lt = 314.90 [1 – e−0.089 (t +1.13)]). The ICCAT Atlantic bluefin tuna database contains numerous records of Atlantic bluefin tuna L outside the biological feasibility, and solutions are provided to recognize and remove these outliers based on the application of fixed values of Fultons condition factor (K) between 1.4 and 2.6 and appropriate L-W relationships to correct this situation in the future.

Turkish driftnet fishery for albacore, Thunnus alalunga (Actinopterygii: Perciformes: Scombridae), and incidental catches in the eastern Mediterranean

Albacore, Thunnus alalunga (Bonnaterre, 1788), is a highly migratory epipelagic oceanic species, found mainly in midwater to depths of 100 m, which has a cosmopolitan distribution in all tropical and temperate oceans. As the albacore is a globally important target species, it accounts for close to 200 000 t annually (Golani et al. 2006). The GFCM-ICCAT Expert Consultation Meeting in Bari in 1990 indicated that albacore in the Mediterranean should be considered as a separate stock. Moreover, genetic analyses are currently being carried out to confirm or refute the existence of a separate Mediterranean stock (Anonymous 1995). Driftnet, longline, hand line, and troll are the main gears used and albacore are also occasionally caught by French purse-seiners, by the Spanish coastal artisanal fleet, and by the sport fishery (Anonymous 1995). The driftnet fishery for albacore tuna in the north-east Atlantic developed in the late 1980s, and France introduced the use of driftnets in this fishery in 1986, followed by Ireland in 1990 and the UK in 1991 (Ross and Isaac 2004). Although various countries (including France, Ireland, Portugal, and the UK in the Atlantic, Spain in Gibraltar and Italy in the Mediterranean, and in minimal extent France) were fishing with albacore driftnets until the mid1990’s (Anonymous 1995), the driftnet fishery has been abandoned in all these countries since then. However, Oceana and MarViva (Cornax and Pardo 2009) identified 93 illegal driftnetters in Italy and the main ports used for this fishing in Morocco during 2008. In the early 2000s, the European Union and the International Commission for the Conservation of Atlantic Tunas (ICCAT) enforced a recommendation prohibiting the use of driftnets in the Mediterranean followACTA ICHTHYOLOGICA ET PISCATORIA (2012) 42 (2): 131–135 DOI: 10.3750/AIP2011.42.2.06

The effect of the lunar phase on the catch per unit effort (CPUE) of the Turkish swordfish longline fishery in the eastern Mediterranean Sea

Background. The swordfish, Xiphias gladius Linnaeus, 1758, is a pelagic and highly migratory species distributed in the Atlantic, Indian, and Pacific oceans as well as in the Mediterranean Sea. Swordfish fishing has been carried out in the Mediterranean with longlines, gillnets, harpoons, and traps since the Roman times. Although information is available on the influence of the lunar phase on the catch per unit effort (CPUE) for the swordfish longline fishery in the Atlantic and Pacific oceans, the data concerning the Mediterranean is rather limited. The aim of this study was to examine the relation between the lunar phase and the swordfish CPUE, based on data from Turkish longline fisheries, targeting swordfish in the eastern Mediterranean during the 2008–2016 fishing seasons. Material and methods. We monitored randomly the daily fishing activity of longliners based at the ports of Fethiye and Özdere during 2008–2016. A total of 86 surveying operations were carried out, including 79 in the area between Fethiye and Alanya, the remaining ones were in Özdere in the southern Aegean coasts along the eastern Mediterranean Sea. The effect of the lunar phase on the swordfish catch rates, expressed in terms of kg · 1000 hooks–1, was examined by means of the Generalized Additive Modelling (GAMs) techniques. Results. The observed CPUE rates ranged from 0 to 700 kg · 1000 hooks–1. The mean swordfish CPUEs in the dark and light periods of the lunar cycle were equal to 178.10 ± 19.01 and 175.27 ± 19.56 kg · 1000 hooks–1, respectively. Although no significant differences among phases of the Moon were found (P > 0.05), CPUEs differed significantly between years (P < 0.05). Conclusion. It seems that the mechanism linking swordfish CPUE variations with the lunar cycle involves several factors, making difficult the identification of direct relations. Further studies are needed to better clarify the impact of the lunar phase on the longline gear, considering also additional parameters, such as light transition, prey abundance, physico-chemical characteristics of the marine environment, and the soak time of the gear.

Technical characteristics of deep-sea rod and reel for groupers in Fethiye (Aegean Sea)

Bu calisma, Fethiye yoresinde derinsu orfozlari icin kullanilan bir olta tipinin teknik ozellikleri ve avlama yontemini ilk kez rapor etmektedir. Bu yontem bolgede sadece iki balikci teknesi tarafindan kullaniliyorken, bircok amator balikci yildan yila bu balikciliga katilmaktadir.