aquaria aquarium emmen sea cucumber Sea-cucumber zoo Asian black chinese cucumber diet fish food health healthy japanese korean meat natural nutrition raw rice salmon sashimi sea seafood appearance balate brine bêche-de-mer colors colours display displayed echinoderms edible elongated fish market for sale harvested holothurian home cooking human consumption leathery marine animals market medicinal medicine ready for purchase rubbery scavengers sea cucumbers sea food selection shapes shopping Sizes skin slimy slippery smell surface textured textures tough trepang variations varieties water wet wet market worm-like