Evaluation of fishery resources utilization in the western Indian Ocean based on mean trophic levels

Abstract:

The West Indian Ocean is an important fishing area in the world. The evaluation of fishery resources utilization is an important basis for scientific management and sustainable development of the resources.According to the FAO’s catch data from 1950 to 2018 and trophic level of fish species in the western Indian Ocean, the mean trophic level (MTL) of 69 years and fishing in the balance index (FiB) were analyzed to evaluate the development and utilization of fishery resources.The results showed that the catch showed an increasing trend from 1950 to 2018 in the western Indian Ocean, and the increasing trend could be divided into three stages including 1950-1982, 1983-2005 and 2006-2018. The catch of small sardines was the highest in the species from the western Indian Ocean.The MTL of the catch decreased first, then increased, and then stabilized during 1950 to 2018.According to the above three phases, its average MTL were 3.49±0.14, 3.71±0.06 and 3.71±0.03 respectively, and the high MTL of the catches (TL>3.25) were 4.04±0.04, 4.09±0.04 and 4.13±0.01 respectively.It is found that the average trophic level fromthe high MTL (TL>3.25)catch and total catch show the similar changing trend (P<0.001).The FiB index showed an upward trend on the whole, and the mean FiB of three stages were 0.099 8±0.165 9, 0.804 1±0.184 9 and 0.978 2±0.067 0 respectively.According to the analysis, the early catch was relatively low in the western Indian Ocean from 1950 to 1982, and the MTL and FiB showed a fluctuating decreasing trend with the increase of the catch of low trophic level such as sardines.From 1983 to 2005, with the increase of high trophic level catch, MTL and FiB showed a gradually increasing trend.From 2006 to 2018, MTL and FIB were relatively stable at a high value.The results show that the fishery resources in the western Indian Ocean are in good condition, the ecosystem structure and function are stable, and the resources of western Indian Ocean still have great development potential.