From selective tidal transport to counter-current swimming during watershed colonisation: an impossible step for young-of-the-year catadromous fish?

Abstract

Key-words:Behavioural shift, Migration, Anguilla Anguilla, Liza ramada, tidal limit During watershed colonisation by catadromous species, two main phases have been identified: tidal estuary crossing and non-tidal river colonisation. Fishes use selective tidal-stream transport (STST) during the first phase of this colonisation, and counter-current swimming during the second phase. Therefore, catadromous species have to achieve a behavioural shift, from STST to constant counter-current swimming. This has not yet been observed, and the location and period of this shift is still unknown. Our experimental protocol aimed to mimic the spatial progression of crossing the tidal limit within a 3-week experiment. Two catadromous fishes, thinlip mullets and European eels, were initially subjected to current reversal every 6.2 h during the first week. A gradual tidal distortion was performed during the second week, and fishes were submitted to a unidirectional water current during the third week. Our results reveal that all catadromous species use STST as far as possible within the tidal limit. At this point, in this experimental study, no young-of-the-year (YOY) fishes shifted from STST to constant counter-current swimming. This confirms that the behavioural shift occurs later, and that the second part of the upstream migration, counter-current progression, is performed by larger, older fishes and not YOY fishes. RÉSUMÉPasser d'un transport tidal sélectif à une nage à contre-courant : une étape impossible pour les poissons catadromes de l'année ? Mots-clés :Bascule comportementale, Migration, Anguilla Anguilla, Liza ramada, limite tidale Deux phases principales ont été préalablement identifiées lors de la colonisation des bassins versants par les migrateurs amphihalins thalassotoques. Ces espèces utilisent le transport tidal sélectif (TTS) lors de la première phase dans l'estuaire tidal, puis une nage active à contre-courant lors de la seconde phase dans les rivières non tidales. Les thalassotoques doivent donc réaliser une bascule comportementale entre ces deux comportements. Cette bascule n'a pas encore été observée directement. Sa localisation ainsi que sa période restent inconnues encore à ce jour. Notre protocole expérimental visait à reproduire en mésocosme la traversée de la limite tidale, lors d'une expérience longue de 3 semaines. Des individus de deux espèces thalassotoques, le mulet porc et l'anguille européenne, ont été initialement soumis à une renverse de courant toutes les 6,2 heures durant une semaine. Puis une déformation progressive de l'onde de marée a été effectuée Article published by EDP Sciences T. Trancart et al.: Knowl. Managt. Aquatic Ecosyst. (2014) 412, 04 lors de la seconde semaine. Enfin, lors de la 3 e semaine, les poissons n'ont été soumis qu'à un seul courant unidirectionnel. Nos résultats suggèrent que les thalassotoques utilisent le TTS aussi loin que possible, jusqu'à la fin de la limite tidale. Arrivés à ce point, dans notre étude expérimentale, aucune juvénile de l'année n'a...

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

“…Once entered, glass eels remain in the area under marine influence in the initial phase of recruitment, consistent with the results obtained by other authors (e.g. White and Knights, 1997;Feunteun et al, 2003;Edeline, 2007;Trancart et al, 2014). During this phase, glass eels are still unpigmented, and they undergo a period of adaptation that involves onset of pigmentation, swim bladder activation and beginning of active swimming, or the so called counter-current swimming (Trancart et al, 2014).…”

“…White and Knights, 1997;Feunteun et al, 2003;Edeline, 2007;Trancart et al, 2014). During this phase, glass eels are still unpigmented, and they undergo a period of adaptation that involves onset of pigmentation, swim bladder activation and beginning of active swimming, or the so called counter-current swimming (Trancart et al, 2014). 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.…”

“…The features of this decline have been summarized by Harrison et al, 2014, who also review behavioural and environmental processes, modulating juvenile eel recruitment patterns to the catchment level. The success and entity of such a process depends in fact not only on global scale processes (Knights, 2003;Kettle and Haines, 2006;Bonhommeau et al, 2008;Pacariz et al, 2014;Guti errez-Estrada and Pulido-Calvo, 2015), but also on local environment conditions related to the hydrological, morphological and meteorological features of a specific site, which modulate space and time dynamics of the ascent (Gascuel et al,1995;Arribas et al, 2012;Harrison et al, 2014;Trancart et al, 2014;Aranburu et al, 2015).…”

RAD Sequencing Highlights Polygenic Discrimination of Habitat Ecotypes in the Panmictic American Eel

“…In the extreme case of the Lake Ontario-Upper St. Lawrence River, these freshwater rearing have more than 1,300 additional kilometers to travel during their migrations in both directions. Also, many freshwater individuals need to swim against the current to reach their rearing areas, whereas brackish/saltwater eels can rely more on selective tidal transport [17]. This suggests that energetic and locomotion costs that differ greatly between ecotypes are reflected in the genome and GO terms that define the genetic differences.…”

Wetenschappelijke onderbouwing en ondersteuning van het visserijbeleid en het visstandbeheer: Onderzoeksprogramma visserij 2016 - eindrapport

“…Voor het Vilaine-estuarium schatte Briand et al (2005a) de relatieve bijdrage van deze actieve fractie tot de totale glasaalpopulatie op ongeveer 10%. Trancart et al (2014) stellen zelfs dat deze omslag van passief getijtransport naar actieve migratie niet voorkomt bij de 0 + -jaarklasse (glasaal) en dat de kolonisatie van niet-getijgebonden rivieren door oudere vissen (elvers en gele palingen) met betere zwemcapaciteiten geschiedt. Verschillende onderzoekers besluiten dan ook dat palinggoten ter hoogte van de getijdenbarrières weinig relevant zijn (Bult & Dekker 2007, Lafaille et al 2007).…”