Habitat selection and diet in two species of pipefish from seagrass: Sex differences

Pipefishes Stigmatopora argus and S. nigra were collected dunng field expenments to test responses of seagrass-associated fishes to changes in the height and density of seagrass leaves. Most pipefish greatly preferred long, high-density seagrass leaves to short or low-density leaves. The exception was female S. argus, which were found in thinned long seagrass as often as in dense long. Females of both species had fuller guts than males Irrespective of habitat, consistent with the idea that males suffer some loss of feeding efficiency due to adaptations for brooding young. Sex ratios measured at 2 different spatial scales were biased in favour of males for both species. For both species the clutch size of male pipefish with completely filled broodpouches was, on average, the same as the number of developing ovanan eggs in females. These results are revlewed in light of current sexual selection theory.