Seasonal, spatial and gear-related influences on relationships between retained and discarded catches in a multi-species gillnet fishery

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“…Depending on the mesh sizes, the discard amount had its maximum value in 32 mm and minimum in 40 mm. Gray et al (2005) reported that retained and discard catches were lowest in the smallest mesh size and our findings are also in accordance with their results. The number of discard species by mesh sizes was highest in 32 mm and lowest in 40 mm.…”

“…Throughout the study, while 82.02% of the caught species had commercial value, 17.98% of this species was discarded. Gray et al (2005) reported the discard rate in gillnets as 6.2%. The differences in the results (discard rates) can be attributed to the species compositions resulting from regional differences, technical characteristics of nets and fishing strategies.…”

“…While there are many studies on bycatch and discards in gillnets (e.g. GodØy et al, 2003;Gray et al, 2005;Bettoli and Scholten, 2006;Shester and Micheli, 2011), in Turkey, bycatch and discard studies were in general related to trammel nets (e.g. Aksu, 2006;Gökçe and Metin, 2007;Akyol, 2008;Metin et al 2009).…”

Mitigating discard mortality from dusky flathead Platycephalus fuscus gillnets

“…In general, the immediate and 3 h retrieval of gillnets (Methods 2 and 3) are permitted throughout the year, mainly targeting sea mullet Mulgil cephalus, while overnight deployments (Methods 1 and 4) are restricted to between April and October, during which time the deeperwalled configurations are used to catch both species above, but also luderick Girella tricuspidata and yellowfin bream Acanthopagrus australis. Irrespective of their deployment, nearly all gillnets are between 375 and 1450 m in length, and typically fished by 1 person from a powered dory.In recent years, concerns over the discarding of unwanted catches (termed 'bycatch') by NSW gillnetters, and the potential for associated negative impacts on the stocks of important species, resulted in fisherydependant surveys to firstly quantify bycatches (Gray 2002, Gray et al 2004, 2005a, and then examine technical solutions to improve the selectivity of problematic gillnet configurations (Broadhurst et al 2003, Gray et al 2004. Because gillnets typically select fish across a narrow range of sizes (see Hamley 1975 for a review), much of the latter work simply involved increasing the existing minimum size of mesh (80 mm in most configurations) to correspond to the maximum girth of legalsized individuals of the key targets (Broadhurst et al 2003).…”

“…Because gillnets typically select fish across a narrow range of sizes (see Hamley 1975 for a review), much of the latter work simply involved increasing the existing minimum size of mesh (80 mm in most configurations) to correspond to the maximum girth of legalsized individuals of the key targets (Broadhurst et al 2003). Based on a clear negative relationship between the catches of undersize Acanthopagrus australis and Girella tricuspidata (both < 25 cm total length [TL]) and the size of mesh, the minimum was increased to 95 mm for deep-walled configurations deployed for longer than 3 h (Gray et al 2005a).While 95 mm mesh has reduced the bycatches of many gillnetters, 80 mm is still permitted in nets that are either set and retrieved within 3 h to catch Mugil cephalus, or left overnight to target Platycephalus fuscus, primarily because these fish have much narrower girths at their minimum legal sizes (MLS; 30 and 36 cm TL, respectively) than other important species, including Acanthopagrus australis and Girella tricuspidata. Consequently, at times at least some proportions of the catches from 80 mm nets are discarded, including juveniles of the above economically important species, as well as yellowfin leatherjacket Meuschenia trachylepis, flounders Pseudorhombus spp.…”