Destruction of sea cucumber populations due to overfishing at Abu Ghosoun area, Red Sea

Abstract

Sea cucumber populations in the Egyptian Red Sea have been exploited by uncontrolled fishery with no management takes place. The sea cucumber populations were surveyed at Abu Ghosoun area, Red Sea, during three period intervals in 2000, 2006, and 2016. In 2000 and 2006, the total number of recorded species was 13 species, which decreased to only 7 species in 2016. The population density of sea cucumber were greatly affected by overfishing and showed a uniform pattern of very low density in 2006 and 2016 after the high density recorded in 2000. Holothuria atra recorded the highest density that reached 128.1 ind./100 m2 in 2000 and decreased to 120.4 ind./100 m2 in 2006 and 87.4 ind./100 m2 in 2016. The dramatic decrease in densities was observed in other recorded species as in Thelenota ananas which decreased from 48.1 ind./100 m2 in 2000 to only 5.6 ind./100 m2 in 2006 and completely disappeared during 2016. The total abundance of all sea cucumber species recorded during 2000 was 13,880 individuals, which decreased to 7700 individuals in 2006, then to only 2420 individuals in 2016. The remaining individuals in 2016 comprise only 17.4% of the original population recorded in 2000, which means that 82.6% of the sea cucumber populations were lost during the 16 years. The study showed a difference in relative abundance between different species and years. In 2000, the relative abundance ranged between 3.03% for Actinopyga miliaris and 18.44 for Holothuria atra. In 2006, the relative abundance ranged between 2.08% for Stichopus horrens and 31.17% for Holothuria atra. While in 2016, the relative abundance ranged between 0% for several species and 71.9% for Holothuria atra. The total biomass recorded showed high decrease from 10,373.8 kg in 2000 to 5461 kg during 2006 and 1379.6 kg in 2016. The study revealed that sea cucumber species diversity and density were much reduced from 2000 to 2016. It also revealed a difference in dispersion among the different years of investigation, indicating the high influence of overfishing on the sea cucumber populations.