Factors affecting recruitment of glass eels into the Grey River, New Zealand

Abstract

The arrival pattern of glass eels of the shortfin eel Anguilla australis and longfin eel Anguilla dieffenbachii was studied over a two successive migration seasons in the Grey River, South Island, New Zealand. Fishing was carried out on selected nights during September to November, for 3 h per night during 2000 and 2001. The number of shortfin glass eels exceeded longfins in both years; earliest glass eels (September) were larger than later glass eels (November), and longfins larger than shortfins, but there were significant differences in size between years for both species. Environmental variables affecting recruitment differed between years, but common variables for both years were sampling date, time after high tide (incoming tide preferred), time after sunset and moon phase; the influence of moon phase appeared to be expressed both through tides (spring tides preferred) and moonlight. During the year of higher discharge variability, both increasing discharge and increased turbidity were also important.

Oceanic and local environmental conditions as forcing mechanisms of the glass eel recruitment to the southernmost European estuary

“…That is, the variability in the annual recruitment depends on the quantity and physiological state of glass eels that arrive to the coast as well as the local conditions (Jellyman and Lambert, 2003). In the Guadalquivir River, recruitment was higher in years with higher rainfall and westerly and southerly wind mixing indices, whereas a negative correlation was observed between northerlies and the annual estuarine glass eel recruitment.…”

“…It has been widely reported that environmental factors, such as moonlight, river flow, tidal cycle, conductivity, salinity and water temperature, affect the freshwater migration of glass eels and elvers on northern European coasts (Gascuel 1986;Elie and Rochard, 1994;Ciccotti et al, 1995;White and Knights, 1997;Jellyman and Lambert, 2003;Edeline et al, 2005). However, there is very little information on the glass eel in the southernmost estuaries of its European distribution area (Arias and Drake, 1990;Drake and Arias 1991;Zompola et al, 2008).…”

Un Outil D’aide Á La Gestion De L’anguille : Le Tableau De Bord Anguillle Du Bassin Loire

“…ou anthropiques (soutien de débits réservés par exemple), ils doivent être pris en compte pour interpréter et relativiser les variations des indicateurs d'état de la population et pour moduler les indices de potentiel d'accueil et de libre circulation. Des facteurs comme la température, le coefficient de marée, le débit, la phase lunaire influencent le flux migratoire des civelles (voir par exemple DE CASAMAJOR et al, 1999 ;JELLYMAN et LAMBERT, 2003) et des anguilles de dévalaison (voir par exemple FEUNTEUN et al, 2000b ;DURIF et al, 2003). Leur prise en compte doit être intégrée dans la définition des protocoles devant permettre des mesures de flux.…”

Stage-specific distribution models can predict eel (Anguilla anguilla) occurrence during settlement in coastal lagoons

“…The definitive settlement, when elvers move across nearby areas under freshwater influence, confirms the high importance of the freshwater appeal for driving movements of juvenile eels. According to Tosi et al (1990), Tosi and Sola (1993) and Sola and Tongiorgi (1996), this is due to specific olfactory cues attracting elvers, which has also been pointed out by Jellyman and Lambert (2003) and Crivelli et al (2008). Freshwater appeal causes young eel to move differently in lagoons with respect to what is observed in estuarine and river systems.…”

“…The influence of tidal cycles and moonlight on glass eel movement has been well documented (Sorensen and Bianchini, 1986;Ciccotti et al, 1995;Jellyman and Lambert, 2003;Crivelli et al, 2008;Zompola et al, 2008;Sullivan et al, 2009). In our study, even though, glass eels have been observed in respect with new moon and first quarter moon, model predictions did not reveal a correlation.…”