The effect of structural enrichment in hatchery tanks on the morphology of two neotropical fish species

Abstract

Reared fish differ from wild fish in several aspects, including morphology, because they are adapted to captive conditions that are totally different from natural conditions. To minimize the influence of the hatchery environment on the morphology of fish, the use of environmental enrichment through the incorporation of natural designs in captivity, has been proposed. In the present study, we performed the physical structuring of fish farming tanks to verify the enrichment effect on the morphology of two species of neotropical fishes: Prochilodus lineatus and Brycon orbignyanus. Each species was subjected to four different treatments over two months: tanks with submersed logs, with artificial aquatic plants, with both structures and without any structure. Results showed that the structural enrichment had a strong effect on the morphology of the cultured fish, which varied with each species analyzed and with the type of structural complexity added to the tanks. There was an increase of morphological variability in the population of P. lineatus and an increase of the average length in the population of B. orbignyanus. This shows that the environmental enrichment is capable to induce morphological differentiation through phenotypic plasticity, probably generating phenotypes more adapted to exploiting a complex environment.Peixes cultivados diferem de peixes selvagens em vários aspectos, incluindo morfologia, pois são adaptados às condições de cativeiro, que são totalmente diferentes das condições naturais. Para minimizar a influência do meio de cultivo sobre a morfologia dos peixes, o enriquecimento ambiental, através da incorporação de 'designs' naturais em cativeiro, tem sido proposto. No presente estudo, foi realizada a estruturação física de tanques de piscicultura para verificar o efeito deste tipo de enriquecimento ambiental sobre a morfologia de duas espécies de peixes neotropicais: Prochilodus lineatus e Brycon orbignyanus. Cada espécie foi submetida ao longo de dois meses a quatro diferentes tratamentos: tanque com troncos submersos, tanque com plantas aquáticas artificiais, tanque com ambas as estruturas e tanque sem qualquer estrutura. Os resultados demonstraram que o enriquecimento estrutural teve forte efeito sobre a morfologia dos peixes cultivados, o que variou de acordo com a espécie analisada e com o tipo de complexidade estrutural adicionada aos tanques. Houve aumento da variabilidade morfológica na população de P. lineatus e aumento do comprimento médio na população de B. orbignyanus. Isto mostra que o enriquecimento do ambiente de cultivo é capaz de induzir a diferenciação morfológica através de plasticidade fenotípica, provavelmente gerando fenótipos mais adaptados à exploração de um ambiente complexo.

Structural and Social Enrichment: Effects on the Morphology of a Tropical Hatchery Fish

“…They attribute the lower feeding efficiency to the macrophytes, that obstruct light, restrict predators in their movement and increase the chances for mobile invertebrates to escape from an attack. In another recent study, we found that artificial macrophytes hamper the development of curimba, decreasing the condition factor of individuals (Saraiva and Pompeu, 2014). However, in the present study, the condition factor of curimba in the tanks treated with macrophytes was not significantly affected, but this may be a result of the higher mortality and consequent lower density in these tanks.…”

“…In the present study, by comparing tanks with and without piapara we were able to detect an effect of this species on the morphology of curimba. By comparing tanks without structures to those with different structure types, we could also demonstrate the structural enrichment effect, in the same way as in a previous study (Saraiva and Pompeu, 2014). Since the same pattern of results was found in both studies we can certify, despite the lack of replications, that the changes in fish morphology were a result of the treatment itself and not of a possible tank effect.…”

“…Logistical problems prevented us to replicate the treatments. However, previous study at the same hatchery and using the same tanks and the same types of structural enrichment have indicated that there was no significant effect of the tank on the morphology of fish (Saraiva and Pompeu, 2014) In tanks with piapara, to maintain the fish density of 150/m², postlarvae were added at a ratio of 100 curimba to 50 piapara per square meter. All the postlarvae were added to the tanks on a single day (in December 2011), three days after hatching.…”

Environmental enrichment in fish aquaculture: A review of fundamental and practical aspects

“…However, changes in behavioural responses to structural enrichment depend on ontogenetic life‐stages of reared fish 52 . Furthermore, Saraiva and Pompeu 53 demonstrated that structural EE (submerged logs and artificial aquatic plants) can induce morphological differentiation in two Neotropical species ( Prochilodus lineatus , Brycon orbignyanus ) through phenotypic plasticity, potentially generating phenotypes more adapted to exploiting a complex environment. In addition, the use of nets in hatchery and nursery tanks is known to be widely used in gilthead seabream ( Sparus aurata ) and European seabass ( Dicentrarchus labrax ) farms (Arechavala‐Lopez P. pers .…”

Effect of environmental enrichment on the body shape of the pumpkinseed

“…(2010) have found significant differences in body and head shapes of 3-spine stickleback Gasterosteus aculeatus , depending on whether fish were reared in an environment with just gravel or in an environment enriched with large stones and artificial plants. Similarly, according to Saraiva and Pompeu (2014) , structural enrichment has a strong effect on some morphological traits such as a smaller size of the head and enlarged fins in the Neotropical fish species Brycon orbignyanus (suggesting a differentiation that facilitates manoeuvrability). Although changes are much more likely to occur at early developmental stages than in later ones ( Meuthen et al.…”