Odnos otolıta ı velıčıne medıteranske skuše (trachurus medıterraneus, steındachner, 1868) u severo-ıstočnom delu Crnog mora

Mediterranean horse mackerel has an important commercial value for the Turkish fisheries. It was the second important species after anchovy in Turkey with a 115000 t production in 1986. Due to collapse of anchovy stocks since the early 1990’s, amount of catch has gradually decreased and production of horse mackerel in 2004 and 2005 decreased to 6301 t and 8287 t, respectively. It was 2651 t and 5982 t in the Southeastern Black Sea in respective years. Knowing the relationship between otolith length and fish length provides important information in determining the length of fish from the otoliths found in archaeological areas and stomach of the predators, validate ageing studies and mainly for the back calculation for the length of the rare species (Echeverria, 1987; Panfili and Tomás, 2001). Moreover, in some fish species the fish age can be determined by the otolith weight due to a high correlation existing between these two parameters (Pawson, 1990; Mardinale et al. 2000). There are no studies on ageing of Mediterranean horse mackerel in the Black Sea. There is only one comprehensive research on the relationships between otolith dimensions and fish length which has been carried out on Trachurus mediterraneus in the Sea of Marmara (Bostanci, 2009). Polat and Kukul (1990) studied ageing methods of Atlantic horse mackerel Trachurus trachurus in the Black Sea. In the present study it was aimed to derive all possible relationships between otolith dimensions and fish size using samples of Mediterranean horse mackerel caught in the South-Eastern Black Sea. These models can be used to estimate fish age from selected independent parameters especially for the routine monitoring studies for fisheries management. As a result, mean otolith length, width and weight of all samples was derived as 4.321 mm, 2.507 mm and 0.0109 g, respectively. Otolith length (OL)-otolith weight (OW), otolith length (OL)-otolith width (OWi), fish total weight (TW)-otolith weight (OW), fish length (TL)-otolith length (OL), otolith length (OL)-age (A), otolith weight (OW)-Age (A), otolith length (OL)-fish total weight (TW), otolith weight (OW)- fish length (TL), otolith width (OWi)- fish length (TL), otolith width (OWi)- otolith weight (OW) relationships were derived as OW=0.0006OL1.8971(n=394, r=0.853), OWi=0.923+0.367OL (n=551,r=0.814), OW=0.0039+0.0003TW (n=455,r=0.868), OL=1.0035+0.2458TL (n=557,r=0.811), A= 3.3398+0.4554OL (n=531, r=0.711), A=0.0051+0.0021OW (n=453, r=791), TW=0.5218OL2.473 (n=531, r=0.774), TL=8.1884+598.31OW (n=453, r=869), TL= 0.5874+5.635, OW (n=551, r=0,793), OW=0.031+5.635OWi (n=551, r=0.793), respectively. Regarding the relationships between fish and otolith size the highest correlation was found between fish length and otolith weight (r=0.869). It was also observed that there are significant differences between same relationships derived from the two research studies due to work on the samples obtained from different habitats as Sea of Marmara and the Eastern Black Sea

Strane vrste ı njıhov utıcaj na Crno more

The Black Sea, a unique fragile ecosystem, has been under the threat of pollution, climate change, invasive alien species and overfishing over many years. Combined impacts of these threats caused serious problems in the Black Sea ecosystem, fisheries economy and welfare of Turkish fishermen by reduction of the catch of commercial fish species, decrease in biodiversity, loss of habitats, increased food competition of endemic species and related problems in the food web by changes in various trophic levels. In this presentation the impacts of the alien invasive species will be explained on certain species basis in the Black Sea. Unintentionally introduced new species to a certain area are known as invasive species. Alien species that become invasive are considered to be a main direct drive towards biodiversity loss across the globe. In addition, alien species have been estimated to cost global economies hundreds of billions of dollars each year (CBD, 2011). Some of the alien species i.e. Rapana venosa, Anadara inaequivalvis, Mnemiopsis leidyi, Beroe ovata, Mya arenaria, Balanus improvisus, Mugil soiuy, Potamopyrgus jenkinsi caused significant impacts on the Black Sea ecosystem and fisheries. All kinds of impacts due to invasive species had a big effect on the reduction of total fish production in the Black Sea as predation, food competition and major destruction in the food web. There are many other species introduced to the Black Sea from phytoplankton to top predators. Some of the invasive alien species and their impacts in the Black Sea are summarized in Table 1. Research studies on the impacts of alien species to the ecosystem and fisheries economy are very limited in the Black Sea. In order to support the ecosystem recovery in spite of all types of negative impacts for the sustainable management of the natural resources, it is very essential to understand, analyze and take urgent management measures regarding all aspects of the ecosystem. New research studies in the Black Sea should be focused on prey-predator relationships, reproduction and growth rates of invasive species, relationship between their distribution and environmental factors, assessment of limiting factors, natural barriers and mechanisms, etc

Length-weight relationships of 28 fish species caught from demersal trawl survey in the Middle Black Sea, Turkey

This study provides updated the length-weight relationships and Fulton's condition factor of 28 fish species belonging to 23 families from the Black Sea. Samples were collected along the depths between 0-100 meters by demersal trawl surveys conducted seasonally from May 2017 to September 2019. A total of 83,885 specimens were collected. The length-weight relationships and Fulton's condition factor, minimum, maximum and mean lengths, total weights, descriptive statistics, and growth type were provided for all the species. The results indicate that LWR parameters of b varied from 2.2039 to 3.737 and Fulton's condition factor varied between 0.004 and 1.18. These findings could be useful for monitoring and management of sustainable fisheries and habitat health

Meristic and morphometric characteristics of the Black Sea salmon, Salmo labrax Pallas, 1814 culture line: an endemic species for Eastern Black Sea

The Black Sea salmon Salmo labrax Pallas, 1814 is an essential species for the Turkish aquaculture sector, given increasing trends of the annual productions. To date, there are few studies on meristic and morphometric characteristics of this species. In this study, the fifth filial generation of the species was specified and studied for meristic and morphometric characteristics. The results obtained in this study were compared with available literature and a similarity was found between the study specimens and wild individuals. The morphological characteristics of any cultured species is valuable especially when a new culture generation is formed and therefore this study outcomes may provide important information to the literature