Linking individual behaviour and migration success inSalmo salarsmolts approaching a water withdrawal site: implications for management

Abstract

-Seaward migration of immature salmonids (smolts) may be associated with severe mortality in anthropogenically altered channels. Few studies however, have identified distinct behaviours that lead to exposure to adverse habitats or even unsuccessful migration. This study used high resolution telemetry to map migration routes of Atlantic salmon (Salmo salar) smolts approaching a water withdrawal zone associated with an aquaculture facility in a lowland river. Individual smolts were tagged with an acoustic transmitter and released upstream of the water withdrawal zone. A trap was installed downstream of the water withdrawal zone. The trap captured all smolts that passed the water withdrawal zone. The tracking results confirmed previous studies on Pacific salmon showing that Atlantic salmon smolts may perform milling behaviours (i.e. upstream excursions and circular swimming behaviour) in anthropogenically altered channels. Non-milling and milling smolts were compared. Smolts performing milling behaviours covered a larger area (m 2 ) and experienced an increased probability of entering the water withdrawal zone, considered an adverse habitat. Finally, smolts were identified as either passing (67%) or non-passing (33%) the water withdrawal zone based on the recapture data from the trap. In total, 20% of the non-passing smolts entered the aquaculture facility. Several behavioural traits differed between the remaining (80%) non-passing smolts and the passing smolts. In particular, time spent near the water withdrawal zone correlated negatively with the probability of passage. These links between individual behaviours and exposure to adverse habitats and passage probability may be applied to improve management of salmonid populations.

Movement patterns of seaward migrating European eel (Anguilla anguilla) at a complex of riverine barriers: implications for conservation

“…Known tag locations demonstrated a minimum accuracy of <1 m which is comparable to other studies (Brown et al 2009;Svendsen et al 2011). This enabled optimal positioning of the hydrophones and quantification of detection efficiency.…”

“…; Thorpe & Morgan 1978;Tytler et al 1978 for Salmo salar). Peake & McKinley 1998), actively seek high velocity zones (Svendsen et al 2007) and avoid rapid accelerations of flow (Kemp et al 2005;Enders et al 2009;Svendsen et al 2011). Peake & McKinley 1998), actively seek high velocity zones (Svendsen et al 2007) and avoid rapid accelerations of flow (Kemp et al 2005;Enders et al 2009;Svendsen et al 2011).…”

Can behavioral fish-guidance devices protect juvenile Chinook salmon (Oncorhynchus tshawytscha) from entrainment into unscreened water-diversion pipes?

“…During these holding periods, fish may repeatedly encounter water diversions located along the riverbank. Svendsen et al (2011) determined that a water diversion caused Atlantic salmon (Salmo salar) to slow their migration speed and perform milling behaviors with fish swimming back upstream or in circles near the water-diversion entrance. The longer fish remained near the diversion, the more likely they were to enter it and fail to migrate.…”

Identifying when tagged fishes have been consumed by piscivorous predators: application of multivariate mixture models to movement parameters of telemetered fishes

“…In contrast, Svendsen et al [14] utilized a trap below a water diversion to verify that after tagging Atlantic salmon smolts, the fish tracks were indeed from tagged smolts. Given the dynamics of our study area, the recapture of tagged fishes was impractical.…”

“…For example, to maximize efficiency of their seaward migration, emigrating smolts will likely exhibit linear movement that is oriented with the direction of flow [12]. This movement would be characterized by shallow turning angles [13,14] and is similar to the exploratory behavior found by Morales et al [10]. In contrast, the track of a foraging predator would likely exhibit steep turning angles and a non-linear trajectory, consistent with patrolling or prey-searching tactics or an encamped behavior characteristic of a fish holding in feeding lanes or eddies.…”