66 MARCH 2018 • WORLD AQUACULTURE • WWW.WAS.ORG fishing licenses, collecting fry from collection stations, redistributing fry to inland lakes (Qarun and Wadi Al Rayan), producing statistical information of fish production and consumption, and providing technical support to farmers and fish farms when needed. In 2014, Lake Qarun was the source of the highest recorded fish supply at 4,518 t/yr, compared to other water bodies in the Fayoum area (GAFRD 2017). Tilapia, mullet and sole are the most collected fish type (Table 1). Catches increased gradually from 2006 until they peaked in 2013 and 2014, and then suddenly decreased in 2015. In 2015, fish production in Lake Qarun decreased to 1,124 t/yr, related to high fish mortalities, and declined further to 873 t/yr in 2016. The main reason for the high fish mortalities was the appearance of an unusual external crustacean parasite heavily infesting all fish species in Lake Qarun during the summer of 2015. Parasitological examination indicated that two isopod species, identified as Nerocila orbignyi and Renocila thresherorum, heavily infested the branchial cavity of all collected fish (Fig. 2). Water analysis indicated high salinity levels and high water temperature that enabled survival and reproduction of the parasite. The main reason behind the presence of the isopod parasites in this closed lake was a biosecurity breach during routine fry transfer from wild natural sources in the sea to the lake. In addition, the physicochemical character of lake water provided ideal conditions for the parasite to acclimate and attack almost every kind of fish in When people think of Egypt, three things come to mind: it is an ancient civilization, mostly covered by dry land, and home to the Nile River. Many do not realize that Egypt has a network of large lakes (more than ten) that represent an enormous wildlife habitat. These lakes also support a large fishing industry, representing about two-thirds of the inland catch, with fish captured from the Nile River representing about one-third. Lake Qarun is a closed lake with a high evaporation rate, located in the Fayoum depression in the western desert of Egypt. It is one of the country’s prime sites for migratory and water birds. The water source of the lake is saline agricultural drainage that enters through two principal channels: the Bats drain, flowing into the eastern basin, and the Wadi drain, entering the western basin (Fig. 1). There is an ongoing stocking program that includes tilapia (Oreochromis spp.), mullet (Mugil spp.), sea bream (Sparus aurata), seabass (Dicentrarchus labrax), sole (Solea vulgaris) and shrimp (Metapenaeus and Penaeus spp.) by the General Authority for Fish Resources Development (GAFRD). Stocking is done with fry collected at various stations around the country that are then redistributed to the lake. The GAFRD is part of the Ministry of Agriculture and Land Reclamation and has authority for development and management of fishery resources (including aquaculture) in all lakes, with the exception of Lake Nasser. These responsibilities include issuing Mass Mortalities in Lake Qarun, Egypt Associated with an Isopod Infestation Nevien Abdelkhalek, Mohamed El-Adl, Mohamed Salama, Moustafa Al-Araby and Ahmed Hafez FIGURE 1. Location map of Lake Qarun in Egypt with its relevant sources. FIGURE 2. The collected fish revealed the presence of isopoda parasites (red arrows) infesting the branchial cavity of Tilapia zilli (A), Mugil cephalus (B) and Solea vulgaris (C). Photo: Nevien Abdelkhalek. The main reason for high fish mortalities was the appearance of an unusual external crustacean parasite heavily infesting all fish species in Lake Qarun during the summer of 2015. The main reason behind the presence of the isopod parasites in this closed lake was a biosecurity breach during routine fry transfer from wild natural sources in the sea to the lake. In addition, the physicochemical character of lake water provided ideal conditions for the parasite.
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