Mortalities of fish escaping from square and diamond mesh codends in the Aegean Sea

Determining the severity of skin injuries of red mullet, Mullus barbatus (Actinopterygii: Perciformes: Mullidae), inflicted during escape from trawl codend

“…Previous survival studies carried out at the same site (Metin et al 2004, Düzbastılar et al 2010a, 2010b, 2010c did not investigate the role of scale and skin damages on fish mortality. Metin et al (2004) performed only a visual post-mortem examination for red mullet within the first 24 h following capture.…”

“…The transportation time was shorter than 1 h. At the end of the observation period, the cages were lifted up, and survivors were counted, and their lengths were measured. The 9 days monitoring period was chosen because the majority of the deaths have been shown to occur within the first 48 to 72 h after capture (Metin et al 2004, Düzbastılar 2010b. A photograph was taken of both flanks of each specimen using a digital camera (Nikon D200) and examined to determine major injuries.…”

“…However, there have hitherto been only a few studies (Metin et al 2004, Düzbastılar et al 2010a, 2010b, 2010c attempting to estimate the mortality of fish escaping from the trawl codend in the Mediterranean. Thus, there is little available information on how escape mortality during commercial bottom trawling is affected by factors such as: codend mesh size and shape, fish size, species-specific variation, and the type of skin injury (Suuronen 2005).…”

“…Thus, there is little available information on how escape mortality during commercial bottom trawling is affected by factors such as: codend mesh size and shape, fish size, species-specific variation, and the type of skin injury (Suuronen 2005). However, a number of studies have addressed escape mortality for some demersal fishes from the Aegean Sea, such as: red mullet, Mullus barbatus Linnaeus, 1758; annular seabream, Diplodus annularis (Linnaeus, 1758); blotched picarel, Spicara maena (Linnaeus, 1758); brown comber, Serranus hepatus (Linnaeus, 1758); and black goby, Gobius niger Linnaeus, 1758; and the causative role of several factors such as the mesh size and shape, fish size, species-specific variation, and water temperature (Metin et al 2004, Düzbastılar 2010a, 2010b, 2010c.…”

“…Deformation of scales and skin, which are protective physical barriers, can increase the susceptibility to infection (Rottmann et al 1992). Metin et al (2004) and Düzbastılar et al (2010b) observed scale loss and sores on red mullet individuals held in cages after escape. However, an assessment of injuries to red mullet individuals escaping from trawl codends has not been made in the Mediterranean Sea.…”