Dynamics of Resources of the American Eel, Anguilla rostrata: Declining Abundance in the 1990s

Abstract

The American eel (Anguilla rostrat) is a catadromous panmictic species that has long provided important fisheries (Eales 1968). These resources have been heavily utilized across its North American range (Fig. 1). However, from the mid-1980s throughout the 1990s, commercial catches declined dramatically as value and fishing effort increased. This change is confirmed by most scientific indices, especially those that are long term and fishery independent. Indeed, the earliest and best documented index comes from the number of juvenile eels ascending the eel ladder in the St. Lawrence River (Fig. 1) at the Moses Saunders Hydroelectric Dam (Fig. 2) (Castonguay et al. 1994a; Casselman et al. 1997b). As the ladder is an index of recruitment at the extremity of the population range of this panmictic species, Casselman and Marcogliese (2000) and others have contended that it provides evidence of general species decline, reflecting inadequate juvenile recruitment to maintain distant stocks. Decline of the long-valued, highly productive St. Lawrence River-Lake Ontario (SR-LO) stock is of particular concern because it is the largest source of old (1960s, maturing silver phase, range 13-42 years, mean 19.7 ± 1.1 years), uniformly large (915 ± 24 mm, 1902 ± 166 g), fecund spawners. Fecundity is directly related to size (Barbin and McCleave 1997), and Castonguay et al. (1994a) concluded, from the relative size of the watershed, the largest available to the species, that the SR-LO stock could contribute up to 19% of the overall female spawning stock. The decline in this stock’s contribution could cause a major loss of escapement of fecund spawners from the continent, accelerating deteriorating recruitment and species decline and resulting in diminishing overall resources.