How to improve foraging efficiency for restocking measures of juvenile Baltic sturgeon (Acipenser oxyrinchus)

Abstract

Atlantic sturgeon (Acipenser oxyrinchus), also known as Baltic sturgeon, is considered missing or extinct in German waters. Current conservation efforts focus on re-stocking activities, but classical hatchery rearing may reduce the fitness of the respective juveniles. In this study, we evaluated if foraging efficiency can be improved by short term training. Over a period of 14 d, we kept individuals of the training group in a raceway and fed them chironomids buried in a small sand spot to stimulate benthic feeding behavior while fish of the control group were fed in tanks without substrate. Thereafter, each fish was transferred to a raceway entirely covered with sand. For feeding, chironomids were randomly buried in the sand. During the first 7 days, trained fish recovered the feed significantly faster than untrained fish of the control group. Gene expression revealed an up-regulation in neurod1 in all brain regions after 14 d of training. Thus, this study suggests that foraging efficiency can be improved through short-time training thus improve fitness upon restocking into the wild.

Reared to become wild-like: addressing behavioral and cognitive deficits in cultured aquatic animals destined for stocking into natural environments—a critical review

“…The aim of these studies is to make the animals feed in the proper areas postrelease. Cámara- Ruiz et al (2019b) not only improved in-substrate foraging behavior of Atlantic sturgeon (Acipenser oxyrinchus), but also demonstrated a possible neurophysiological mechanism behind it as they found increased neurogenesis in the brain, associated with learning and memory in the fish. Krepski and Czerniawski (2019) released bottom-foraging trained brown trout (Salmo trutta) into natural streams and found that bottom-fed individuals had higher growth rates in shallow streams, but interestingly not in deeper streams.…”

“…Some aspects of foraging behaviors are innate and hatchery-reared predators typically manage to feed on live prey, although often with lower efficiency than wild conspecifics (e.g., Paszkowski and Olla 1985, Fjellheim et al 1995, Ellis et al 2002, Seebacher et al 2010. Learning rates are typically rapid when repeatedly exposed to live prey (e.g., Ware 1971, Paszkowski and Olla 1985, Reiriz et al 1998, Cámara-Ruiz et al 2019b), but learning rates can differ for different prey types (Vinyard et al 1982, Stradmeyer andThorpe 1987) and across ontogenetic stages (Donadelli et al 2015). Furthermore, the selection of prey may not be optimal (Reiriz et al 1998).…”

“…Associative Priming Studies.-Some food-training studies apply more complex training schemes with additional aims such as associative priming, where natural food becomes associated with a particular substrate (Cámara- Ruiz et al 2019b) or a specific location in the water column (typically the bottom; Czerniawski 2019, Takahashi et al 2013). The aim of these studies is to make the animals feed in the proper areas postrelease.…”

Estimating predation rates of restocked individuals: The influence of timingof-release on metapenaeid (shrimp) survival.

“…. This can increase predator awareness [22] and promote natural feeding abilities [23], leading to greater survival post-release and hence more effective enhancement strategies.…”

Can juvenile Baltic sturgeon ( Acipenser oxyrinchus ) smell the enemy?

“…In a recent study (Camara-Ruiz, Santo, Gessner, & Wuertz, 2019), an increase of neuroplasticity markers in fish that were trained to feed prey buried in the sand compared to fish that were not trained was observed. Among these markers pcna, neuroD and bdnf are established markers for neuronal activity and neurogenesis and have been used as tools to understand how external stimuli influence the brain (Dunlap, 2014(Dunlap, , 2016Mes, Krogh, Gorissen, Mayer, & Vindas, 2018).…”