Substratum selection by juvenile flounder Platichthys flesus (L.): effect of ephemeral filamentous macroalgae

• Published in: Journal of fish biology 2008-06, Vol.72 (10), p.2570-2578
• Main Authors: Carl, J. D., Sparrevohn, C. R., Nicolajsen, H., Støttrup, J. G.
• Format: Article
• Language: English
• Subjects: flatfishes; flounder; habitat complexity; Marine; Platichthys flesus; sediment; substratum selection; vegetation
• ISSN: 0022-1112; 1095-8649
• DOI: 10.1111/j.1095-8649.2008.01866.x

Selection of substrata representing habitats with or without filamentous vegetation by juvenile flounder Platichthys flesus was investigated in laboratory experiments and a field study to assess the effect of the increasing occurrence of ephemeral filamentous macroalgae in shallow nursery areas and its potential effect on flounder recruitment. In the laboratory experiments, 79% of juvenile flounder (24–99 mm total length, LT) preferred bare sand substrata in comparison to substrata with simulated filamentous vegetation. Substratum preference did not change with fish size. Field sampling using a drop trap (1 m2) in a vegetated (>50% coverage of ephemeral macroalgae) habitat in June, July and August showed small flounder (mean LT= 37·3 mm) were caught more often in samples with less vegetation. In contrast, larger flounder (mean LT= 57·2 and 79·7 mm in July and August, respectively) were more evenly distributed in relation to the distribution of vegetation. The results of this study indicate that the increase in ephemeral macroalgae observed in recent years potentially reduces the quantity and quality of suitable nursery habitats for juvenile flounder, which could have detrimental consequences to the overall recruitment of flounder in coastal areas.