Do the visual conditions at the point of escape affect European sea bass escape behavior?

Abstract

European sea bass (Dicentrarchus labrax), an important species for the Mediterranean aquaculture industry, has been reported to escape from sea cage installations. Fish escapes are caused mainly by operational and technical failures that eventually create tears. Escapees may interact with wild stocks through interbreeding, transfer of pathogens and competition for food. The aim of this study was to examine to what extent the presence of a visible obstacle close to a tear in the net influences sea bass propensity to escape. Fish were initially confined into small sea cages, with a tear on one side. The escape behaviour was tested under experimental conditions. It is clearly demonstrated that sea bass were able to locate a tear in the net pen, immediately after its appearance. Crossings occurred in all cages, in singles or in a series of up to seven individuals. The presence of an obstacle close to the net tear altered the escape behaviour of D. labrax, resulting in a delay that eventually reduced the escape rate. To conclude, it is highly recommended that sea bass cages should be kept internally the culture array. Furthermore, the placement of artificial obstacles close to the sea cages could be an efficient practice that mitigates the escape risk after severe environmental conditions.

Behavioural Differences in Tank-Held European Sea Bass under Dark/Light Environment

“…Both tank exploitation was necessary against undesirable fish density or species biology that is characterized by an elongate body size [24] and a remarkable swimming activity [25]. Intense crossing activity had also been described in laboratory-caged sea bass [26], where crossing in series of several individuals were observed through the net tear. The continuous crossing activity during the study is likely to either search for food or tank exploitation, while comes in agreement with similar results in fisheries study with other species [4] where mackerels, tuna as well as other species tended to move in and out of the illuminated field driven by feeding motivation.…”

Mediterranean Aquaculture and Genetic Pollution: A Review Combined with Data from a Fish Farm Evaluating the Ecological Risks of Finfish Escapes

“…A common behavior of gilthead seabream, Sparus aurata (Linnaeus, 1758) (Teleostea: Sparidea), that leads to escape events is net biting when it is agitated from threats or prey [12,13]. On the other hand, European sea bass Dicentrarchus labrax (Linnaeus, 1758) (Teleostea: Moronidae) usually do not exhibit net-biting or induced-escape behavior and are characterized as more opportunistic concerning escape events [14]. Furthermore, wild predator species may cause enlargement of net holes, new sites' net breakage, and even stress to farmed fish.…”

Σχεδίαση, Ανάπτυξη Και Αξιολόγηση Ενός Απεικονιστικού Συστήματος Πολλαπλών Ανιχνευτών, Για Τη Μελέτη Της Συμπεριφοράς Ιχθύων

“…Both tank exploitation was necessary against undesirable fish density or species biology that is characterized by an elongate body size (Volcaert et al, 2008) and a remarkable swimming activity (Pickett and Pawson, 1994). Intense crossing activity had also been described in laboratory-caged sea bass (Papadakis et al, 2013c), where crossing in series of several individuals were observed through the net tear. The continuous crossing activity during the study is likely to either search for food or tank exploitation, while comes in agreement with similar results in fisheries study with other species (Marchesan et al, 2005), where mackerels, tuna as well as other species tended to move in and out of the illuminated field driven by feeding motivation.…”

“…In particular, the escape-related behavior of fish has been documented in several studies, concerning species interactions with the aquaculture net pen and relevant factors that lure them to cross a net tear (Glaropoulos et al, 2012, Hansen et al, 2008, Moe et al, 2007, Jensen et al, 2010, Papadakis et al, 2013c. Automated quantification of fish bites and escape events has only been realized by the application of specific video monitoring systems.…”

“…In particular, bite activity was studied in the sea bream, a farmed species that regularly interacts with fairly damaged nets (Papadakis et al, 2013b). In addition, because sea bass rarely exhibit any exploratory behavior on the net pen (Papadakis et al, 2013c), the present study only focused on the motivation of fish to cross the net tear. Both experiments were performed over 30 days.…”