Demographic parameters and status assessments of Lutjanus ehrenbergii,Lethrinus lentjan,Plectorhinchus sordidus and Rhabdosargus sarba in the southern Arabian Gulf |
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Authors: | E Grandcourt T Z Al Abdessalaam F Francis A Al Shamsi |
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Institution: | Biodiversity Management Sector, Marine, Environment Agency, Abu Dhabi, United Arab Emirates |
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Abstract: | Demographic parameters and status assessments for L. ehrenbergii, L. lentjan, P. sordidus and R. sarba in the southern Arabian Gulf were established using a combination of size frequency, biological and size‐at‐age data. Defined structural increments consisting of alternating translucent and opaque bands in transverse sections of sagittal otoliths were validated as annuli. The maximum age estimates ranged from 5 years for R. sarba to 14 years for P. sordidus. Growth trajectories were significantly different between sexes for L. ehrenbergii and L. lentjan with females achieving a larger asymptotic size than males. Estimates of fishing mortality rates were less than the target (FSB40) and limit (FSB30) biological reference points for L. ehrenbergii, L. lentjan and P. sordidus indicating that these species were exploited within sustainable limits. Conversely, R. sarba was found to be heavily overexploited and recruitment overfishing may have occurred as the fishing mortality rate was considerably greater than the limit reference point and the relative spawner biomass per recruit was 6.4% of the theoretical unexploited level. Due to restrictions in the available data set, the presented results require confirmation from specific studies on natural mortalities and from growth estimates based on more extended size spectra, avoiding any size selective sampling method. |
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