@Pertinax, that is true ... I know. I was purely speaking from a husbandry/animal management perspective. However, if Longleat do not clean up their act here at some point the EAZA/BIAZA marine mammal TAG will come back to haunt them for failing to provide a quality habitat.
For what it is worth, I can hardly imagine / see why a freshwater lake with discharge from a herd of hippos, a natural riverine flow with native vegetation and species is A) a healthy and safe environment for marine mammals and B) is ecologically damaging practice in terms of water quality and impacts upon the local environment.
BTW: I will consult the EAZA guidelines on marine mammals where this pertains to whales/dolphins and pinnipeds ..., but I do see "big issues" for Longleat Safari Park with their sealions down the line! As an aside, I think/am afraid that this moment may be sooner rather than later ....!
When I read the area already has a Eurasian beaver population of 30+ I was both amazed and shocked at the number. I wonder how large the riverine habitat is available to these typical marshland and river habitat mammals.
NOTA BENE: Re-establishing the species in the Netherlands started early 1990's and in the first few years with the reintroduction of a number of pairs over a 3 year time frame, and then the next cohorte ..... elsewhere.
I present here the case study for the original reintroduction in the Dutch Biesbosch from 1988-1991. Within this timeframe 42 Eurasian beaver from the Elbe river in BRD (Germany) were translocated to the Biesbosch. First dispersal from the re-introduction area only happened from 1995, so a good 8 years after the first arrivals.
SOURCE:
https://www.zoogdiervereniging.nl/sites/default/files/publications/Lutra 46(2)_Sluiter_2003.pdf
It seems to me that re-occupation in the riverine habitats around Longleat really happened much faster ....! I would be interested to hear and learn of any case studies from the UK on Eurasian beaver reintroduction projects and their progress! I would really appreciate if any UK Zoochat Forumsters would have more on this....