Reproductive Strategies in the Stone Loach Noemacheilus barbatulus

Abstract

Egg volumes and larval weights of loach, N. barbatulus (L.), from Konnevesi, an oligotrophic lake in central Finland were 2.4 to 3.1 times greater than those from the Frome, a calcareous stream in southern England [UK] and between 2.4 and 4.0 times those of other European populations. In Konnevesi most spawning occurred over 10-12 days shortly after ice melt when somatic condition was lowest. Other populations spawn successive groups of eggs over several months and somatic condition remains stable. At the commencement of spawning Konnevesi loach had heavier gonads than Frome fish but fecundity was only one tenth as high. Konnevesi loach in age groups III to V accounted for 94% of population fecundity whereas Frome fish in age groups I and II accounted for 95%. The proportion of new tissue allocated to reproduction in Konnevesi loach was close to zero until age III but subsequently rose from 0.36 to 0.52 of the total in VI group fish. In the Frome it rose from 0.35 in I group of 0.66 in III group fish. These contrasting reproductive strategies are discussed in relation to life-history theory and the environments in which these populations live.