The Efficiency of Selective Tidal Stream Transport in Glass Eel Entering the Gironde (France)

Abstract

Traditional estimation of migration speed is based on telemetry or marking of individual fish. Only a few numbers of fishes (or batches) are followed, often over short periods of time. We propose a method based on capture data from the professional fishery. It is applied to glass eel (Anguilla anguilla) in the Gironde basin (France).Migration speed is estimated using 2 methods: a rough method based on the analysis of seasonal abundance peaks for two métiers and a more precise method of cross-correlation, which compares speeds between several fishing areas. The methods are coherent and lead to mean migration speed ranging from 3 to 4 km/day.We define an index of efficiency of migration using selective tidal stream transport (STST efficiency index) as the ratio of the observed migration speed to the potential speed (flood tide current speed and swimming speed). For the glass eel in the Gironde basin this index ranges between 0.15 and 0.19. The glass eel behavior, which can explain this low value, is reviewed.Our STST efficiency index can be successfully applied for many fish or crustaceans using selective tidal stream transport. It can also be used for one species to compare results obtained on different basins. Key-words:Migration speed, sequential fishery, cross-correlation, selective tidal stream transport, glass eels, Anguilla anguilla, STST efficiency index. EFFICACITÉ DE LA MIGRATION DES CIVELLES ENTRANT DANS LE BASSIN DE LA GIRONDE EN UTILISANT UN TRANSPORT SÉLECTIF TIDAL RÉSUMÉLes méthodes traditionnelles d'estimation de la vitesse de migration reposent sur la télémétrie ou les techniques de marquage. Seulement un nombre restreint de poissons (ou lots de poissons) sont ainsi suivis, souvent sur un temps court. Nous proposons une méthode basée sur les données de capture de la pêcherie professionnelle. Elle est appliquée au cas de la migration de la civelle (Anguilla anguilla) dans le bassin de la Gironde (France).

Short-term responses of glass eels transported from UK to small Belgian streams

“…Nevertheless, such qualitative precocious monitoring is important to better understand the stocking process and glass eel adaptations. The dispersion outside our limited study site probably occurred by swimming with and against the current or passive migration by flooding rather than only higher natural mortality (Beaulaton and Castelnaud, 2005;Bureau du Colombier et al, 2009). Considering the migration rate of elvers to be 0.64 km per day observed in non-tidal rivers (White and Knights, 1997), some individuals in the stocked young eels in the three streams may leave the reference stretches in just 1 day, as already noted by Pedersen (2009).…”

Annual variability in upstream migration of glass eels in a southern USA coastal watershed

“…During migration, they encounter a series of environmental conditions, particularly a salinity gradient of 2.0-15.0 psu as they enter eastern Albemarle Sound to 0.0-0.3 psu as they enter Roanoke River. We did not calculate the transport time of glass eels from Oregon Inlet to Roanoke River but this migration could last from 30 to 40 days (Beaulaton and Castelnaud 2005). However, if glass eels enter Beaufort and Oregon Inlet at the same time and size, the difference in size of glass eels entering Beaufort Inlet and Roanoke River may be because of environmental conditions (water temperature) encountered by glass eels that are favorable to growth as they migrate through Albemarle Sound.…”

“…New markets and increased demand for juvenile eels in the aquaculture industry have increased fishing effort on the early life stages (Meister and Flagg 1997). Additional factors influencing the sustainability of eel populations include disease, pollution, dam passage, habitat fragmentation, changes in hydrologic regimes and climate change (Castonguay et al 1994a, b;Beaulaton and Castelnaud 2005). Because of the recent population declines and increasing demand for eels, fisheries managers must have information of stock dynamics to ensure widespread sustainability of the fishery.…”

Efficiency of a dual density studded fish pass designed to mitigate for impeded upstream passage of juvenile European eels (Anguilla anguilla) at a model Crump weir

“…Adult eels migrate from rivers to oceanic spawning grounds, thought to be in the Sargasso Sea, while the larval life stage (leptocephali) uses ocean currents to return to continental waters (Tesch 2003). As they develop into glass eels, they move through estuaries predominately by selective tidal stream transport (McCleave & Kleckner 1982;Beaulaton & Castelnaud 2005) and embark on active upstream migration in rivers as they metamorphose into the pigmented elver life stage (Chadwick et al 2007). Anthropogenic barriers (e.g.…”