Why Starving CA Sea Lion Pups? Sardine Biomass Lowest In a/l 15 Yrs - "Any Fishing Is Overfishing"
Recent national news stories have shown emaciated California sea lion pups being rescued and admitted to marine mammal rehabilitation centers. The sight of hundreds of withered sea lions is reminiscent of the all-too-recent California sea lion "unusual mortality event" in 2013 followed by a significant number of stranded and dead sea lions last year. Dying sea lions and strandings are becoming less unusual and a more frequent occurrence. In fact, the 2015 sea lion deaths are already on pace to exceed the 2013 numbers. About 70 percent of sea lion pups are expected to die this year before weaning age.
So, why are these pups stranding and dying? It is simple. The sea lions are starving. Nursing female sea lions don’t have enough food to eat; primarily fatty forage fish like sardine and anchovies and they are spending more time foraging, which means less time feeding their pups. In turn the pups are not getting the nutrition they need, and people are finding them stranding on beaches, weak, emaciated and dying.
As the National Oceanic and Atmospheric Administration (NOAA) stated following the 2013 mortality event, these sea lion pups are starving and malnourished due to a “change in the availability of sea lion prey, especially sardines” (NOAA Fisheries 2014). This preliminary finding suggested the sardine population was spawning further offshore, outside of the foraging range of nursing California sea lions. At the same time, however, other key forage fish prey like anchovy and hake are spawning closer to shore or spawning locations are unchanged. So, a shift in the spawning location of sardine alone does not explain the cause. What is happening is that there is an overall decline in the abundance of forage species. Importantly, NOAA scientists are now corroborating the hypotheses that seas lions are starving due to a lack of prey, not just that the prey moved someplace else.
At a scientific conference in December 2014, NOAA scientists reported: In the last decade, key components of sea lion diet have either almost disappeared (anchovy), or decreased in biomass (sardine), while market squid abundance increased…Increasing squid abundance and declining sardine and anchovy abundance, reduced the caloric value of available forage in the last 10 years… Occurrence of numerous malnourished pups may now become frequent as the sea lion population experiences food limitation (McClatchie et al. 2014).
Indeed the sea lion population has been steadily increasing at a rate of over five percent per year and the latest population estimate is that there are over 300,000 California sea lions off the U.S. West Coast (NOAA Fisheries 2015). Nobody knows what the sea lion carrying capacity is (how many sea lions the environment can naturally support), but right now, the population is clearly being limited by the abundance and availability of forage fish.
EDIT
http://oceana.org/blog/why-are-california-sea-lion-pups-starving#
