Trawl codend selectivity estimates for goldband goatfish
Trawl codend selectivity estimates for goldband goatfish
Date
2010
Authors
Madhu, V.R.
Meenakumari, B.
Panda, S.K.
Journal Title
Journal ISSN
Volume Title
Publisher
Society of Fisheries Technologists (India)
Abstract
The knowledge of selectivity of commercially important gears is vital
for effective monitoring, management and sustainable exploitation of
fishery resources. Using selective gears help to minimize the capture of
juveniles by regulating the length at first capture, increasing the yield per
recruit of targeted species and also by helping in the reduction of discards
generated by the fishery (Armstrong et a/., 1990: MacLennan, 1992).
Demersal otter trawls contribute more than a quarter of the global landed
marine catch (estimated at approximately 86 million tonnes in 2004)
(Kelleher, 2005). Due to the frequent use of small mesh size and operating
in the near shore areas, these vessels generate disproportionately high
quantities of bycatch (Andrew and Pepperell, 1992; Kelleher, 2005).
Numerous studies have been carried out to test the utility of alterations
to the size and or shapes of mesh used in the trawls to reduce the bycatch
(Broadhurst, 2000; Madsen, 2007). Mesh opening of the codend (Wileman
et al., 1996), twine diameter (Sala et al., 2007), material used for the
fabrication of the codend (Tokac et al., 2004), speed of the tow (Dahrn
et al., 2002), seasonal changes (Ozbilgin and Wardle, 2002), codend
circumference (Broadhurst and Kennelly. 1996; Broadhurst and Millar,
2009), catch weight (Erickson at al., 1996) and the shape of the mesh
opening (Broadhurst and Kennelly, 1996; He, 2007) are the main factors
that affect the selectivity of the codends. In addition to the above factors,
considerable amount of between-haul variations in selectivity can occur
when the experiments are carried out in replicate hauls (Fryer, 1991). This
variability need to be taken into account so as to make the selectivity
estimates more reliable (Macbeth at al., 2005). Overdispersion in the data
can be quantified using the replication estimate of dispersion (REP), which accounts for the overdispersion due to scaling up of sub-samples and the
between-haul variations (Millar et al., 2004).
Description
Keywords
Goatfish, fishery resources, commercial fishing, harvesting, fishing, trawl codend
Citation
Proceedings of the National Seminar on Conservation and Sustainability of Coastal Living Resources of India, 1-3 December 2009, Cochin, ed.by Meenakumari, B. et.al 360-369