This usually means the fish are either deeper or have migrated out of range. Thus, the overall productivity of the marine environment generally decreases due to the decrease in fish and plankton abundance. As a result, the distribution and quality of prey for some marine mammals decreases. Pinnipeds, which are our primary patients here at The Center, may be affected because they are predators at higher trophic levels in the food chain. During the lactation period, pups rely on the foraging success of their mothers.
Many pups lose weight and have a slower growth rate, and mortality generally increases.
Although adult mortality also tends to in-crease, larger animals are capable of diving to deeper depths in order to utilize reduced prey sources. Larger males that typically migrate anyway, may not suffer the same consequences of those animals that do not tend to migrate. Their smaller size limits their ability to dive deeply or withstand a prolonged period of insufficient nutrition. We saw large increases in emaciated yearling and juvenile California sea lions, those recently weaned and foraging on their own. Whether or not this relationship is coincidental is unknown.