MEPS 182:269-282 (1999)  -  doi:10.3354/meps182269

ABSTRACT: We studied the settlement success and recruitment level of 3 common species of blennoids (Aidablennius sphynx, Parablennius incognitus and Tripterygion tripteronotus ) off the NW Mediterranean coast at 3 localities separated ca 50 km apart, over a period of 4 yr (1994 to 1997). Settlement success is defined as the maximum number of new individuals observed during the settlement period and recruitment level as the number of new individuals at the end of the settlement period. We also determined which descriptive variables of the substratum had a significant influence on settlement, and whether the presence of adults had an effect on settlement. The results from the stepwise multiple regression analysis indicated that the type of substrate cover and the presence of adult conspecifics played a significant part in the abundance of settlers and post-settlers on the rocky shore for all 3 species. The variation in the abundance of settlers of A. sphynx was best explained by the category 'bare rock'. Settlement variance of P. incognitus and T. tripteronotus was mainly explained by the substrate covered with 'small turf of algae'. Field experiments demonstrated a strong relationship between 'bare rock' density and A. sphynx settlement and between 'small turf of algae' density and P. incognitus and T. tripteronotus settlement. However, the strong correlation between settlers and adult conspecifics in the stepwise multiple regression seems to be causal. For the 3 blennoids, preferences for a specific substratum type at settlement can explain, on small scale, the abundance of new settlers in a locality. The maximum density of settlers was only dependent on the amount of preferred substrate available along a transect and independent of the size of a transect. The spatial and temporal patterns of the recruitment level differed from those observed in settlement success. For A. sphynx, no significant temporal and spatial differences were found for settlement success but were for recruitment level. For P. incognitus, no significant differences were found for settlement success, but a significant spatial variation was observed for recruitment level. For T. tripteronotus, the most significant differences were found for settlement success between years, which appeared in patterns of recruitment level. This suggests that the interannual differences were very strong and were maintained throughout the post-settlement period. For this species, significant differences of settlement success were also found between localities, however, they were not maintained over the season. Our results demonstrate that post-settlement processes can alter settlement patterns.

KEY WORDS: Settlement · Recruitment · Population dynamics · Habitat selection · Fish · Mediterranean