Abstract: A fish-cage incubator has a light source for attracting zooplankton therein a mesh barrier that admits zooplankton and excludes predators of fish larvae.

Abstract: A variable buoyancy float/ballast assembly has control means allowing it to sink otherwise floating objects and bring sunken objects to the surface or control their placement in the water column. The assembly can be employed to tension mooring lines, reduce vertical uploads on anchors and dampen mooring line transients.

Abstract: A submersible cage system for cultivating aquatic animals comprises a rigid frame defining a geodesic enclosure, a net supported by the rigid frame to define a water permeable enclosure for the aquatic animals, the rigid frame being rotatable about a horizontal axis, flotation chambers disposed at opposite sides of the rigid frame, the flotation chambers being alternately fillable with a gas or a liquid to increase or decrease, respectively, the cage system's buoyancy, and a mooring for anchoring the frame in a fixed position in a marine environment.