(Mirror Daily, United States) – Hundreds of starving seal pups stranded themselves in California and researchers tried to figure out the reason. The phenomenon has become increasingly common, at it seems that the food resources are to blame. If the mother seals do not find fish that is filled with the appropriate amounts of nutrients, the seal pups will be thinner, malnourished.
Hundreds of starving seal pups stranded themselves in California, and the declining numbers of anchovies and sardines are directly responsible.
According to the government researchers that looked into the problem, the mothers of the malnourished pups are incapable of finding proper food in order to produce enough milk.
The standard food for seals are anchovies and sardines, but when their population is scarce, the marine mammals turn to squid and rockfish instead.
While rockfish provides enough sustenance in order for both the mother and the up to stay alive, they do not contain appropriate amounts of nutritional content. In consequence, the seals produce less quality milk that does not sustain a harmonious development of the pups.
It has been a rough life for California-based sea lions ever since the 1800s. The peaceful mammals were first hunted down by humans that used their oil, meat and fur. Seeing as they are social creatures, the seals were also hurt during fishing operations.
In less than 200 years, the sea lions population reached an alarming 50,000 individuals. That is when Richard Nixon signed the Protection Act for Marine Mammals. After it was placed under federal protection, the Zalophus californianus population managed to reach 340,000 specimens in 2014.
But federal protection is not enough to keep the sea lion population floating. Due to increasingly violent El Nino phenomenon, their basic food source, anchovies and sardines, was scattered, and they were left with squid and rockfish.
In order to find out more about the changing eating habits of female Zalophus californianus, and to establish the reason for the ever increasing number of malnourished pups, researchers monitored the activity of six individuals which were tagged in the 1990s.
According to the data provided by the tracked females, their preferred hunting locations are between Malibu and Big Sur.
The next step was to find out what kind of fish populated that area in the late years. And an NOAA report showed that the majority of prey consisted of rockfish, squid and other small fish species.
The last step was to establish the average weight of seal pups. It seems that during 2004 and 2011, the standard weight ranged from 14.8 to 20.9 kg in the case of female cubs and 17.5 to 23.6 kg for the male ones.
After compiling and analyzing all of the data, the researchers discovered that in the years in which anchovies and sardines were abundant, the pups faired rather well. But when the only food available were rockfish and squids, the cubs were underweight.
Hundreds of starving seal pups stranded themselves in California, and the reason behind this odd migration is the lack of nutritious food for their mothers.
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