Although the spatial resolution of satellite multispectral images approaches that of the important large herring schools, we used an airborne instrument to fly under the frequent cloud cover which would often preclude acquiring satellite imagery during the brief inshore spawning period. The digital images allow us to examine and classify school shapes, which could resolve overlaps in run-timing that are a problem with the current aerial survey estimator. Wide, shallow depth profiles adjacent to many herring spawning areas constrain school depth variability and keep the upper layer of the schools visible. However, variable packing density remains a problem. We generalize our findings to contend that species color adapted to a pelagic environment should be detectable in the green band if part of their life history brings them into shallow nearshore waters.
Ships are in general good radar hard targets since they tend to have large radar cross sections.
They act as efficient corner reflectors returning a large portion of the incident microwave energy and allowing for easy detection under appropriate sea surface background clutter conditions. The ability to image these hard targets can be exploited to monitor and manage the operation of fishing fleets in sensitive or regulated area. SAR images are also very sensitive to the presence of organic substances on the water surface. These materials tend to dampen the small gravity and capillary waves that the SAR responds to. Dampening of these so-called Bragg waves results in very low backscatter and allows for the SAR imaging of slick features formed by these substances under appropriate wind conditions.