The size frequency structure of live mussels and dead shell samples observed in the study area. A – river Nam Long (live mussels; sites NL1–NL5; n = 66); B – river Nam Pe (live mussels; sites NP1 and NP2; n = 12); C – river Nam Long (shells of mussels, died from natural causes; sites NL1–NL5; n = 89); D – river Nam Pe (shells of mussels, harvested by local people; sites NP1 and NP2; n = 79). Differences between all groups are significant by Kruskal-Wallis test: χ2 (H) = 51.5, df = 3, n = 246, p < 0.001.
Discussion