Effects of temperature, stocking density and farming conditions on fin damage in European sea bass (Dicentrarchuslabrax)

Abstract

-This paper presents a non invasive, rapid and reliable way to quantitatively assess fin erosion in sea bass (Dicentrarchus labrax). The method is based on a visual assessment of fin profile and area loss of all fins except the anterior dorsal, on a scale from 0 to 4 in comparison with a perfect fin. The effects of stocking density (SD) and temperature on fin damage were investigated under experimental conditions (100-250 g fish). Over a 4-month period, mean erosion index (mean erosion level of all fins) was 10 times higher at 120 than at 20 kg m −3 , where most fins were undamaged. Damage was also dependent on time and oxygen concentration (35% lower at 53% O 2 saturation than at 105%). Fin condition was also affected by temperature: mean erosion index was 0.22-0.25 at 13-16 • C, but five times higher at 25 • C. Caudal and dorsal fins were always the most eroded. Fin damage was then monitored in a large land-based farm using high SD, and in a small sea cage farm operating at low SD. At the first site, 6 batches of two market size groups were examined: L (850-930 g, 50-80 kg m −3 ) and S (375-400 g, 42-60 kg m −3 ). Fin condition was good in all batches (mean erosion index, 1.1-1.3) and lowest at the highest SD. At the second site, four batches of large fish (350-890 g, 26-24 kg m −3 ) and four other groups below market size (100-270 g, 8-16 kg m −3 ) were examined. Fin erosion was the highest in large fish (mean erosion index, 1.1-1.2) and in the sea cages most exposed to climatic disturbances. In both sites, the most eroded fins were the caudal and dorsal. Differences in other external injuries were also observed between the two sites (less necrosis and more scale injuries in sea cages). The causes of fin damage are discussed in relation to metabolic and/or behavioral adaptations to rearing conditions and the main actions that could be taken to improve fin condition are discussed. L'érosion des nageoires est la plus forte chez les gros poissons (niveau moyen d'érosion, 1,1-1,2) et dans les cages les plus exposées aux perturbations climatiques. Dans les deux sites, les nageoires les plus érodées sont la caudale et la nageoire dorsale postérieure. Des différences de l'état apparent des poissons sont aussi observées entre les deux sites (moins de nécroses et plus de lésions des écailles chez les poissons en cage). Les causes des lésions des nageoires sont discutées, en relation avec les ajustements du métabolisme et/ou du comportement aux conditions d'élevage, ainsi que les principales actions à mettre en oeuvre permettant d'améliorer l'état des nageoires.

Processing traits of European catfish (Silurus glanis Linnaeus, 1758) from outdoor flow-through and indoor recycling aquaculture units

“…Damaged fin condition is a regular phenomenon associated with intensive fish farming (Latremouille, ). It has been recorded, for example, in rainbow trout ( Oncorhynchus mykiss ; St‐Hilaire et al., ; Ellis et al., ), salmon ( Salmo salar ; Jones et al., ), perch (Stejskal et al., ), sea bass ( Dicentrarchus labrax ; Person‐Le Ruyet and Le Bayon, ), cod ( Gadus morhua ; Hatlen et al., ), and many others, and is usually a result of bacterial infection and/or aggressive behaviour of fish cultured at high densities (e.g. Jobling et al., ).…”

Does fin damage allow discrimination among wild, escaped and farmed Sparus aurata (L.) and Dicentrarchus labrax (L.)?

“…Each individual was measured for length and photographed with a tripod‐mounted digital camera with a light source. Fin erosion was determined for all fins according to the fin erosion scale of Person‐Le Ruyet and Le Bayon (), which quantifies the progressive loss in fin area of seabass ( D. labrax ) juveniles and adults. This index is a numerical system based on a visual assessment of fin condition of all fins on a scale from 0 (perfect fin) to 4 (short and dysfunctional fin).…”

“…This index is a numerical system based on a visual assessment of fin condition of all fins on a scale from 0 (perfect fin) to 4 (short and dysfunctional fin). The anterior dorsal fin area of both seabream ( S. aurata ) and seabass ( D. labrax ) were excluded from erosion assessment because they are usually damaged by handling and therefore difficult to assess (Person‐Le Ruyet and Le Bayon, ). The erosion parameters were calculated from erosion levels of all fins as follows: Fin Erosion Index (FEI), erosion level mean of the five fins and each fin separately of all fish sampled per fish origin; Fin Splitting Index (FSI), mean number of splits per fish calculated for all fins and specific fins separately of all fish sampled per fish origin.…”

“…The freshwater percid walleye ( Stizostedion vitreum Mitchill, 1818), and the marine flatfishes Dover sole ( Solea solea Linnaeus, 1758) and Senegalese sole ( S. senegalensis Kaup, 1858) have also been recorded as prone to fin erosion when they are farmed (Clayton et al., ; Smith, ). Person‐Le Ruyet and Le Bayon () investigated fin damage in farmed seabass under various experimental conditions. However, fin erosion in Mediterranean fish such as gilthead seabream ( Sparus aurata Linnaeus, 1758) and European seabass ( Dicentrarchus labrax Linnaeus, 1758) raised in actual farming conditions has only rarely been reported.…”

Factors Affecting Fin Damage of Farmed Rainbow Trout

“…There is a significant body of experimental research which identified that the main factors affecting fin damage are feeding practices, water quality, stocking density and routine handling, not excluding the bacterial infections (3,6,7,8,9). However, despite the experimental approach, there are few research reports that determine the important factors having effect on fin damage and fish welfare under different commercial production systems (5,10).…”