The majority of fish living below 1000m are predatory ambush predators (Richard 2007) and have adapted to use as little energy as possible (Byatt et al. 2001). They hang motionless in the water column, and wait for their prey to come within close proximity of them. Few species migrate to the more productive upper waters (Koslow 1996) due to the sheer distance between the two and the differences in pressure are too great for most species to cope with. As large prey is quite rare to come across, most species have developed large mouths, enabling them to swallow prey at least as large as themselves and have expandable stomachs allowing them to cope with digestion (Haedrich 1996). They have very slow metabolisms (Koslow 1996), meaning they only have relatively low energy requirements and the majority of bathypelagic species hang motionless in the water column, and wait for their prey to come within close proximity of them (Haedrich 1996). Some species have adapted to survive on much smaller prey whilst waiting for more substantial prey to come along. The stomach contents of Malacosteus, a loose-jawed dragonfish, showed that it feeds on a diet of copepods (Douglas et al. 2000) even though it is highly adapted to tackle larger prey.

Species, like the Anglerfish (Lophiiformes) have developed lures which biolumines, attracting organisms towards the light (see Creators of light section for more detail). These exemplify the sit and wait strategy used, as these organisms entice their prey to them. The hairy anglerfish, Caulophryne polynema, (first image in the header) has developed long hairs which act like antennae and are sensitive to vibration in the water. It remains motionless and is able to detect the slightest vibrations in the water, not just with the hairs but also with its lateral line which runs along the side of its body (Byatt et al. 2001).

Figure 11. A Gulper eel, Order Saccopharyngiformes, clearly showing its disproportionately large mouth and long tail (Amazing Sea Creatures)

Perhaps one of the strangest fish observed so far in the deep sea are the Gulper eels (Figure 11), order Saccopharyngiformes. They have a huge mouth, taking up the majority of its body, which enables them to easily swallow prey larger than themselves, feeding mainly on shrimp and squid (Herring et al. 2007).

Leave a Reply