As mentioned, developmental stages of a species may be expected to shift behavior, even though most investigation concerns only the adult stage. Since cottoid and hexagrammoid fishes lack a swim bladder, the planktonic larval and pelagic juvenile stage (if occurring) need to display behavioral solutions to negative buoyancy. In some species those behaviors reflect morphological specializations for the particular life stage, but other species may simply have to swim very energetically, which will affect food requirements and feeding behavior. Schooling only occurs in adults of some of the few pelagic species in these taxa, but larval stages appear capable of schooling in many of the species observed in aquarium settings.
The cryptic appearance of most cottoids, together with bottom dwelling habits, leads to predation threats that require adaptive behaviors. Chance observations have led to the discovery that the tadpole sculpin, Psychrolutes paradoxus, apparently has an emetic flavor that causes predators to cough them out upon ingestion. This species relies first on its cryptic appearance to prevent predation, then secondarily upon its noxious taste to cause rejection by predators.
Even though cottoids lack a swim bladder, they have big extrinsic swim bladder muscles. The buffalo sculpin, Enophrys bison, vibrates when grasped. Another defense behavior in this and other species is the flaring of the gill cover (with the bony suborbital stay) to expose spines that could deter ingestion.
Homing behavior is well documented in cottids that inhabit tidepools. Tagging studies have not been directed as much at subtidal species, but the demonstration of topographic familiarity in tidepool species may extend to other species inhabiting subtidal reefs with significant landmarks.
The existence of homing behavior proves that learned familiarity with surrounding habitat is of significant survival value and that these fish are capable of exploiting that sort of advantage. Seasonal migrations encompass developmental shifts in habitat preference of young stages as well as reproductive behavior of adults.
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