While the Baltic Sea might seem boring and mundane compared to tropical oceans, it has a fairly diverse and very odd assemblage of fish. It’s the world’s largest pool of brackish water, but it’s geologically so young, there are no specialized brackish water species.
So it’s a confusing mix. There are resilient ocean species, often smaller than their oceanic counterparts and unable to breed in some parts of the sea, and just as resilient freshwater fish venturing into the salty parts. Arctic fish mixed with temperate species coming from south. Oceanic fish that once invaded fresh waters and then returned here, now unable to tolerate full ocean salinity.
Fish that give birth, fish whose males get pregnant, fish whose eyes migrate over their heads during their lifetimes, fish that build nests, fish that smell like fresh cucumber. We have everything.
Made for Sieppo, a children’s magazine published by The Finnish Association for Nature Conservation.
There has been much speculation as to the purpose of the sawfish’s saw. Speculation was that they were used to literally saw chunks of meat from large prey such as whales or dolphins. In fact, the saw is lined with thousands of sensory organs that allow the sawfish to detect the electric fields emitted by living creatures, thus helping them track prey. Once a fish is detected, the sawfish will strike the prey with a sideways slash of the saw, stunning it, or else use the saw to pin it to the sea floor. While the saw is not used specifically to cut prey, a fish may be sliced in half by a particularly vigorous swipe. The saw is also used to defend the sawfish against large predators such as sharks, or in battles with rivals.
In contrast to stories of sawfish cutting through the bottom of boats or sawing humans in half, sawfish are known to be docile and harmless animals when left undisturbed.
Fish with no scales, thin gelatinous skin, and a bulbous head? That’s the deep sea for you!
Snailfish (Family Liparidae) have long, tadpole-like bodies with large
heads and small eyes. They live throughout the world’s oceans from the
Arctic to the Antarctic and from the shallow intertidal zone to many
thousands of meters in the deep sea. They eat small benthic crustaceans,
molluscs, polychaete worms, and other small invertebrates.
This
snailfish, Careproctus longifilis, was photographed using ROV Tiburon
3,300 meters (>10,800 feet) deep in the Monterey Canyon. ⠀
Urocyon's Jaunts 2.0 
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