Assessing the importance of food for improving noble crayfish culture conditions

Abstract

Key-words:species protection measures, feeding trials, food preference, crayfish culture, noble crayfish Captive breeding and crayfish culture are considered important measures in species protection activities. Thus, knowledge on optimal feeding of crayfish in captivity is needed in order to secure minimal mortality and prevent detrimental effects to health. To optimize conditions of crayfish prior to subsequent stocking, feeding trials were conducted with the aim of investigating the connection between food intake, food preference and temperature under near natural conditions. During a five-month period, noble crayfish were fed on fish, carrots, algae and chironomid-larvae according to a pre-defined rotation system, whereby the ambient water temperature ranged from 5 • C to 13 • C, following the natural temperature regime. The results of these feeding trials demonstrate a direct correlation between rising temperature and increasing food intake for water temperatures exceeding 8 • C. Food intake is further influenced by the variety of food items available at any one time. The results also confirm that Astacus astacus has a strong preference for fish and that alternation of food types has an impact on consumption. Our results prompt the following recommendations for optimized feeding conditions of crayfish in captivity prior to their release: (1) a balanced diet containing not only plant tissue but also a significant proportion of animal tissue and (2) the amount of available food must be adjusted according to the carapace length of the crayfish. RÉSUMÉÉvaluation de l'importance de la nourriture pour l'amélioration des conditions d'élevage d'écrevisses à pattes rouges Mots-clés :mesures de protection des espèces, L'élevage en captivité d'écrevisses est considéré comme une mesure importante dans les activités de protection des espèces. Ainsi, les connaissances sur l'alimentation optimale de l'écrevisse en captivité est nécessaire afin d'assurer un minimum de mortalité et prévenir les effets néfastes pour sa santé. Pour optimiser la condition de l'écrevisse avant le repeuplement ultérieur, des essais d'alimentation ont été menés dans le but d'étudier les liens entre la prise alimentaire, la préférence alimentaire et la température dans des conditions proches des conditions naturelles. Pendant une période de cinq mois, des écrevisses à pattes rouges

Simultaneous detection of native and invasive crayfish and Aphanomyces astaci from environmental DNA samples in a wide range of habitats in Central Europe

“…At location 29 (Krumme Lanke), we were unable to detect eDNA of any of the five target organisms despite reports of the presence of both F. limosus and P. virginalis somewhere in the lake in the recent past (Linzmaier et al 2018). This might be explained by spatial mismatch (Harper et al 2018) and low ambient temperatures which may have led to decreased activity of crayfish (Bubb et al 2004;Rusch and Füreder 2015) and thus decreased emission of eDNA.…”

Exploring the eDNA dynamics of the host-pathogen pair Pacifastacus leniusculus (Decapoda) and Aphanomyces astaci (Saprolegniales) under experimental conditions

“…The goal of this study was to test the influence of temperature, food availability and crayfish density on the measurable eDNA amount emitted from P. leniusculus and its obligate parasite A. astaci in a mesocosm experiment. We expected rising temperatures and access to food to cause increased crayfish activity (Flint 1977;Rusch and Füreder 2015) and more faecal matter and, thus, also increased shedding of eDNA from crayfish. For A. astaci, we expected that increased crayfish density would naturally lead to increased amounts of A. astaci eDNA, while food availability for the crayfish was not suspected to directly influence the pathogen amounts.…”