An infection of Gyrodactylus anguillae Ergens, 1960 (Monogenea) associated with the mortality of glass eels (Anguilla anguilla L.) on the north-western Mediterranean Sea board of Spain

The association of Gyrodactylus anguillae Ergens, 1960 with the glass eel stage of Anguilla anguilla (L.) (total body length 61.4 +/- 4.9 mm; range 55-70) is reported from the northwestern Mediterranean coast of Spain for the first time. A sample of 12,600 glass eels, caught by professional fishermen operating in the mouth of the rivers Fluvia, La Muga and Ter (north-east Spain), was subject to mortalities of similar to 1.75% of stock/day following transfer to a research facility. Subsequent losses over a 31-day period amounted to 56% of the initial stocked biomass. Although the moderate burdens of G. anguillae/host (20.2 +/- 6; range 11-32) were the primary reason for a subsequent treatment, a simultaneous infection with Trichodina jadranica Raabe, 1958, Trichodina anguillae Wu, 1961 and Ichthyophthirius multi:finis Fouquet, 1876, makes it impossible to attribute the high mortality of glass eels in this case to a single pathogen. A histopathological examination of the gills of moribund fish showed them to be swollen, hyperplastic and necrotic. This study also redescribes G. anguillae, providing for the first time a full 27 character morphometric description of the attachment hooks, and importantly, a photographic record of the armature of the haptor and the male copulatory organ. (C) 2011 Elsevier B.V. All rights reserved.