Challenges of external insemination in a tropical sparid fish, Acanthopagrus berda

Duration of spermatozoa motility and proportion activated were tested under a range of salinities and temperatures in males of the tropical estuarine fish, Acanthopagrus berda, in both laboratory and novel field experiments. A. berda spermatozoa were activated under a wide range of salinities (5–60%) and showed the greatest duration of motility at approximately 30%) in both laboratory and field fish. The duration of activation exceeded 10 minutes at this salinity. However, relatively low activation rates were recorded (50–70%). The long duration of motility, wide range of activation salinities and low proportion of motile spermatozoa may reflect a reproductive style in A. berda of producing at least some motile spermatozoa despite the ambient conditions at spawning. This is discussed in relation to fishes from other habitats and the wide distribution of A. berda