Alternate Title

Effect of Size and Prior Residence on Dominance in Male Seaweed Blennies, Parablennius marmoreus


Parablennius marmoreus is a small bottom-dwelling blenny living on and around barnacles and other encrusting organisms on offshore petroleum platforms in the northern Gulf of Mexico. Males hold and defend cavities which provide cover and spawning sites. Aquarium tests were used to describe the effects of size and prior residence on dominance among adult male P. marmoreus. A size difference of 3 mm [=5% total length (TL)] was usually enough to enable a larger fish to control a single barnacle cavity. A size difference of 7 mm (=10% TL) always made a larger fish dominant. A prior resident was always able to defend his cavity for at least 10 min when challenged by a blenny of equal size. A prior resident was usually able to defend a cavity when challenged by a blenny 3 mm larger, but was displaced by a male 7 mm larger.