A Few Fascinating Fishy Physiological Facts

By Kathleen Rader, Colorado Aquarium Society. Note: originally published in the 1990 Spring/Summer issue of “The Colorado Aquarist”.

Migdalski and Fichter wrote an interesting book entitled The Fresh and Salt water Fishes of the World (1976, Knopf Publishing, 316 pp). They covered every modern family of fish, and also discussed fossil fish, taxonomy, and so on. A distillation of some of the physiology is given below.

Scales: As a fish grows, its scales increase in size, but not in number, although most species of fish are capable of replacing lost scales. The ridges and spaces on some scales can be studied like the annual rings of trees. Scale experts can tell the age of the fish, when it first spawned and the timing of every subsequent spawn, periods of food scarcity, timing of migrations, illness, etc. Only a few scales are needed for this type of study. Vertebrae and associated bones also have growth rings, but the fish must be posted to study them.

Dragonets

by Kathleen Rader, Colorado Aquarium Society. Note: first published in the Autumn, 1990 issue of “The Colorado Aquarist”

If you are looking for a small fish to put in your invertebrate, seahorse, or other salt water tank, take a close look at these little fish. Their natural curiosity, hopping motions, and ability to get in and out of very small crevasses will add spice to your tank watching, not to mention the addition of wild color patterns by some of these species.

Dragonets belong to the Callionymus family, which contains approximately eight genera and over one hundred species, all of which are marine. The four species most commonly seen in the United Sates belong to the genus Synchiropus, although some have been misnamed “goby” or “blenny”. Callionymus lyra, from the temperate waters off Europe, is one of the pioneering fish in marine aquarium keeping, their spawning behavior has been known since the 1800′s.

Poem: Hermit Crabs

By Kathleen Rader, Colorado Aquarium Society. Note: first published in 1988 in issue No 3, of “The Colorado Aquarist.

Have you ever kept a small hermit crab?

About them I’d like now to blab.

        If you overfeed your tank,

        These crabs you can thank,

As they eat everything they can grab.

Fossil Fish

By Kathleen Rader, Colorado Aquarium Society Note: originally published in the 1989/1990 Winter issue of “The Colorado Aquarist”.

Fish were the first animals with a backbone (vertebrates) to evolve. They appeared in the Ordovician (500 million years before present), evolving from an unknown phylum of invertebrates. Fish ancestry is uncertain, but there are few missing links in the fossil record from the first fish to mammals.

The oldest fish fossils are from Ordovician formations in the U.S.S.R. and Colorado. Pieces of the oldest fish were collected a few miles north of the state penitentiary in Canyon City from the Middle Ordovician Harding Sandstones. Lucky collectors can find small bony scales at this locale.

JAWFISH

By Kathleen Rader, Colorado Aquarium Society.  Note: originally published in the early 1990’s in “The Colorado Aquarist”.

Smilers, Monkeyfish, and Goggle-eyed Cods are all names which have been given to these compulsive burrowers. In scientific nomenclature, jawfish belong to the family Opistognathidae, which contains three genera: Opistognathus, Lonchopisthus, and Stalix. Only the first two are commonly kept in saltwater aquariums. These fish are closely related to pygmy basslets and fairy basslets.

Jawfish are found in tropical to temperate waters around the world. At least eleven species live in the western Atlantic; eight of these are known to reside along the east coast of the U.S. They also inhabit the Florida Keys area, the Caribbean, Gulf of California (Sea of Cortez), Pacific, the east coast of Bali in the Indonesian Ocean, and the Great Barrier Reef of Australia. Unlike pygmy basslets, jawfish prefer living in flat, sandy or coral rubbled areas associated with coral reefs.

The Graceful Seahorse – A Unique Fish

by Kathleen Rader, Colorado Aquarium Society. Note:  first published in the early 1990’s in “The Colorado Aquarist”.

In Medieval times, seahorses were dipped in wine and fed to condemned prisoners as a deadly poison. Some believed that the ashes of seahorses, when combined with honey and vinegar, would cure most illness. Living seahorses dipped in oil of roses were supposed to be good for chills and fever; others used them as aphrodisiacs or to cure baldness. Today, the seahorse is kept in home aquariums to relieve stress.

Habitat: People are surprised to learn that seahorses live in water as far north as Norway. They are found in the Atlantic, Pacific, Indian and Southern Oceans, the Gulf of Mexico, Caribbean, Red Sea, Black Sea, North Sea, Mediterranean and the English Channel. Most seahorses reside in heavily vegetated areas of seaweed, turtle grass or eel grass, in shallow coastal waters that have a sandy or muddy bottom. They are also found in masses of floating seaweed (i.e. sargassum) which can carry them hundreds of kilometers. A few specimens have been retrieved from depths of 600 feet (183 m). They are found in normal marine to brackish (up to 40% fresh) water at temperatures of 43-86oF (6-30oC).

Common Aquarium Bunch Plants

by Kathleen Rader, Colorado Aquarium Society. Note: originally published in the early 1990’s in “The Colorado Aquarist”.

Stores often sell what they call bunch plants. These usually consist of a bundle of plant stems that are held together by a rubber band or lead weight. They are propagated as cuttings. When they become too tall, or thick, they can be pruned back and the pruning pieces can be replanted.

To plant most bunch plants, break the ends off to give the stem a fresh cut, strip the lower inch or so free of leaves and plant them into the gravel. It is usually best to anchor the recently planted cuttings to give the roots a chance to develop. Each plant should be slightly separated from the bunch so that light and water can reach the stems and leaves at the base of the plant.