A comparison between acoustic and bottom trawl estimates to reconstruct the biomass trends of sardine and anchovy in the Strait of Sicily (Central Mediterranean)

•We analyzed the correlation between the biomass indices of sardine and anchovy derived from hydro/acoustic surveys and the MEDITS survey carried out in the Strait of Sicily.•The two surveys data on sardine and anchovy were highly correlated.•We estimated the catchability coefficients for sardine and anchovy of the MEDITS survey.•MEDITS survey sampled only a very reduced part of the available biomass of small pelagics (1.1–1.6%) along the trawling line.•MEDITS data can be used to investigate the population dynamics of the stocks of sardine and anchovy in the Mediterranean.

We evaluated the information on stock abundance of sardine and anchovy collected during the MEDITS trawl survey in the north sector of the Strait of Sicily (central Mediterranean Sea). A comparison between the temporal trends in biomass, derived from the MEDIAS hydro-acoustic surveys carried out along the south coast of Sicily since 1998, and the corresponding MEDITS index of biomass of the two species was performed. The two time series appeared highly correlated (r = 0.85) depicting a very similar temporal trend in biomass for both sardine and anchovy. We also used the biomass index calculated from the hydro-acoustic surveys to estimate the MEDITS catchability coefficient q for the two species per year. The annual variability of q was rather high. The average q value was 0.016 (CV = 60%) for sardine and 0.011 (CV = 55%) for anchovy, respectively, indicating that the bottom trawl net sampled only a very reduced fraction of the biomass of small pelagics (1.1–1.6%) available in the trawled area.Our results indicated that the use of MEDITS trawl survey data might represents an important source of information on the stocks of sardine and anchovy in the Strait of Sicily complementary to the MEDIAS acoustic surveys.