That Fish Blog – Aquarium Advice and Information

With this weeks passing of Earth Day 2008, I thought I would write a blog about this great article that I had read recently on www.sciencedaily.com. Some of the darkest days in U.S history involve the nuclear weapons use and testing during and after WWII. Most people learned about the bombs dropped on Japan during WWII in history class, or from family members who lived in that era.

Much less well known nuclear testing was done in the years following WWII as the cold war escalated, and the demand for bigger and bigger bombs grew. From 1946 to 1958 the U.S. Government conducted nuclear bomb tests on the remote Pacific Island Group of Bikini Atoll, which is part of the Marshall Islands. In 1954 the U.S. detonated, what was at the time, the largest hydrogen bomb ever tested. The bomb was code named Castle Bravo, and was 15 megatons (1,000 times more powerful that the bomb dropped on Hiroshima). The blast vaporized 3 islands, raised the water temperature to 55,000 degrees, and left a crater that was over a mile wide and more that 200 feet deep. Needless to say, there was nothing left of what was a thriving tropical island group and surrounding reefs.

Enough of the bad news, this story has a happy ending. Recently a group of international scientists returned to Bikini Atoll to see what was there, almost 50 years later. Plant life on the surface had returned, but is still contaminated with radiation (don’t eat the coconuts). What the group found underwater was truly amazing. As they planned their dive into the Bravo Crater, expectations were running wild. The last time the area was surveyed it looked like part of the moon, and was irradiated.

What they found was a thriving coral reef ecosystem that had completely self seeded itself in the once barren wasteland. Porites corals that reached 25ft in the water, huge formations that looked like trees reaching for the surface. The belief is that water currents from untouched neighboring areas brought larval corals to Bikini, where they settled and matured. The corals had recolonized as much as 80% of the habitat in some of the areas studied.

Compared to studies performed at Bikini prior to the testing, the results show that there has been a serious impact on the diversity of corals to the area. The new study showed that 40 species that were documented to have been there prior to testing, where no longer there, and appear to be locally extinct. I found it amazing that what was there had reclaimed space that had felt the worst of what human kind can offer.

This news shows that, given the chance, reefs can recover from even the most severe destruction. Maybe by looking at the species that are thriving in the Bravo Crater, we can use them to as a guide to recolonizing reefs that have been destroyed by shipping, fishing, and pollution around the world. The main thing that I took from the story is that if we as a society can get our act together as far as protecting our natural resources, that Mother Nature can fight back pretty hard if we let her.

Until Next Blog,

Dave

The blind cave fish is found in only one cave, La Cueva Chica (the “Little Cave” – the entrance is only 15 feet wide) near Pujal, in San Lois Potosi, Mexico (related species have since been found in other caves). This fact alone should grant it special status among fish keepers, but there is much more to distinguish it – including a rare glimpse at fish adaptation in progress. Apparently, fish with normally developed eyes live in a nearby river, the Rio Tampaon, and are regularly swept into the cave by the current. There, deprived of light and the need for sight, the eyes degenerate. As time goes on, their descendents are born with gradually more reduced eyes, until the eyeless form emerges. Although I have not read evidence of it, I imagine that inter-breeding with eyeless fish already in the cave may hasten the process.

Fish in pools nearest the cave’s entrance rely upon flies, spiders and other invertebrates for food, while those deep inside subsist upon bat guano, dead bats and, I would venture a guess, fleas and other invertebrates that fall from the bats’ fur.

Please welcome back Frank Indiviglio to That Fish Blog. Frank gives his unique perspective on another interesting, sometimes aquarium inhabitant, the crayfish.

Freshwater crayfish, found on all continents except Africa and Antarctica (the southeastern United States, home to 80% of the world’s species, is a hotspot of crayfish diversity), are often purchased as an “oddity” or scavenger to add to the aquarium. However, these active Crustaceans make fascinating pets in their own right and are well worth more attention. I will write more about the specifics of crayfish care in future articles, but would now like to recount my experience with the maternal instincts of one species, the red swamp crayfish, Procambarus clarkii.

It is difficult to house crayfish in groups, as they tend to consume tank-mates that have recently molted (newly-molted crayfish are soft and defenseless). I was, therefore, fortunate in having the opportunity to observe a female with her young in an aquarium. I came across her while she was traveling overland (they do this on occasion) between ponds at the Prospect Park Zoo in NYC. In typical crayfish fashion, several dozen young clung to the swimmerets (feathery organs) on her underside. (Note: the red swamp crayfish is native to the southeastern USA but widely introduced elsewhere. Non-native crayfish cause serious problems in many parts of the world – please do not release unwanted pet crayfish).

Established in a 5 gallon aquarium, the female soon became quite bold and allowed me a peek at her version of maternal care. Any disturbance caused her to rear up, claws extended towards the threat – she definitely seemed more aggressive than crayfish I had kept in the past. The young remained on the swimmerets for over two weeks and then began making short feeding forays on their own but, to my surprise, returned unerringly to their mother after eating. At this point they also began to scamper about the rest of her body, sometimes covering most of her head from view. Knowing of this creature’s pugnacious disposition, I wondered when her “patience” would reach its limit. That limit came after about three weeks, when she promptly began devouring the prodigy she had so carefully nurtured until then. The survivors took refuge in the hiding spots (cracked clay flower pots) that I had provided for them, after which I moved the group to a larger aquarium.

A number of crayfish species are readily available and do well in aquariums. Particularly interesting are stream-dwelling forms, such as the red-tip crayfish, Orconectes erichsonianus, which seem determined to re-arrange every stone in their tank in an effort to establish the perfect home. Others you might consider are the P. alleni, a blue strain of which has been developed for the pet trade, dwarf species such as O. compressus, and the bright blue Australian yabbie, Cherax quadricarinatus.

I’ll write again soon and highlight other species. Until then, I’d appreciate hearing about your own experiences.

A good deal of interesting information, including a key to help you identify the crayfish you may come across, is sponsored by the Carnegie Museum of Natural History:
www.iz.carnegiemnh.org/crayfish/Keys/index2.htm

Thank you, Frank.

I’d like to welcome Frank Indiviglio back to That Fish Blog for another interesting post. Although they’re amphibians, we’ve seen so much of the African Clawed Frog in the aquarium trade, I thought this was appropriate here. Enjoy!

I’ve always been interested in the process by which a species becomes established as a pet. Interesting stories abound, none more so, perhaps, than that of the African clawed frog, Xenopus laevis. Hailing from southern Africa, female clawed frogs were (somehow!) found to possess an unusual trait – exposure to a pregnant woman’s urine causes the immediate release of the frog’s eggs! Dwelling in a harsh habitat, females must be ready to breed on short notice, and nearly always have eggs ready to be fertilized. This, combined with the ease of maintaining them in the lab, soon led to their widespread use in the Hogben Pregnancy Test.

Millions of these frogs were imported to the US in the 1940’s, with many finding their way into the pet trade. Unfortunately, they also made it into local waterways, and today are well established in several states, including Texas, California and Arizona. Ravenous predators, clawed frogs have been implicated in the declines of a number of invertebrate, amphibian and fish species. Recent research also indicates that this species may responsible for starting the worldwide Chitridiomycosis fungal epidemic that is threatening scores of amphibian species.

Feral populations of African clawed frogs are also to be found in Mexico, Chile, France, Italy, Java, Japan, Indonesia, Great Britain, the Ascension Islands and elsewhere. Despite the species’ origins in warm fresh water, one population has adjusted to life in the underground wells of a castle in England, where the water rarely tops 50F, while another group thrives in brackish ponds (they tolerate 40% seawater) in Orange County, California.

These tongue-less, claw-bearing, aquatic frogs make fascinating pets (they are, however, illegal to own in some states). One kept by my frog-enthusiast mother attained 21 years of age, and the published longevity record is 30 years. Unlike most frogs, they will accept non-living food, and thrive upon Reptomin food sticks and frozen fish foods. I’ll discuss the care of clawed frogs and their relatives, African dwarf frogs, Hymenochirus spp. and Surinam toads, Pipa spp., in a future article. Until then, please write in with your questions and observations. Thank you. Until next time, Frank.

You can learn more about this frog’s spread into non-native waters at:
http://www.issg.org/database/species/search.asp?sts=sss&st=sss&fr=1&sn=xenopus&rn=&hci=-1&ei=-1&x=25&y=3

Thanks again for the great article Frank! If you’re interested in reptiles or birds, Frank also contributes to That Reptile Blog and That Avian Blog.

Until Next Time,

Dave

I’d like to take time to welcome Frank Indiviglio to That Fish Blog. Frank is a former Bronx Zoo Zoologist, author and conservationist who’s worked with everything from fish to elephants. He’ll share his unique insights and work with various species on here, as well as the newly created That Reptile Blog & That Avian Blog. Welcome Frank!

Today I would like to pass along some interesting facts concerning fish you may be familiar with. I’ll focus mostly on aquarium trade species, with a few others added for good measure. I’ll add to the list in future articles. Enjoy, and please share your own store of unusual facts with us.

Finding a mate in the dark, featureless expanses of the deep sea poses quite a difficulty. Male benthic anglerfishes, such as Ceratias uranoscopus and related species, solve this dilemma by biting onto the first female they encounter. Thereafter, the male’s internal organs degenerate and he remains fused, by his mouth, to the female – surviving on nutrients circulating in her blood and periodically releasing sperm to fertilize her eggs!

Unique among the world’s fishes, male sticklebacks (small fishes of the family Gasterosteidae that inhabit marine, brackish and fresh waters), use kidney secretions to glue plant materials together when constructing their enclosed, bird-like nests. This behavior, along with their zealous protection of the eggs, helped spur the development of the aquarium hobby in Europe in the 1700s.

Cichlids found in Africa’s Lake Malawi are among the most enthusiastic of nest builders. Although measuring but 6 inches in length, males of one species create circular sand mounds that can exceed 3 feet in diameter, while another excavates 10 foot wide pits. Up to 50,000 such structures may be constructed in the same general area by a displaying group, or “lek” of males.

Marine damselfish, such as Stegastes nigricans, are unique in practicing a form of underwater “farming”. Pairs form territories around beds of marine algae (“seaweed”) and drive off fishes, shrimp, crabs and other creatures that show interest in this favored food.

Clownfish, such as the commonly kept percula clownfish, Amphiprion percula (or its cousin, the false percula, A. ocellaris, of “Nemo” fame) live unharmed among the tentacles of sea anemones — marine invertebrates that sting and consume other similarly-sized fishes. Anemone tentacles respond with a sting upon contact with any alien body, but are prevented from stinging themselves by chemicals in the mucous that they secrete. The clownfish, it seems, produces the same chemical in its own mucous and hence is not recognized as food.

Fishes lack external ears but do have inner ears that pick up the water pressure changes which accompany sounds. Aided by the Webarian Apparatus, an organ that connects the
inner ear to pressure-sensitive gas in the swim bladder, species such as carp and goldfish hear quite well and can communicate through vocalizations (perhaps it is not so odd to talk to your pet after all!).

Among the animals that are kept by people for their fighting abilities, none are as small as brackish-water fishes known as wrestling halfbeaks, Dermogenys pusilla. These thin, 3 inch-long warriors are the subject of staged matches in betting parlors throughout Thailand and Malaysia. Fights rarely result in injury, except to the wallets of losing bettors!

Despite popular belief, koi, Cyprinus carpio and goldfish, Carassius auratus, are not closely related. Goldfish, the first of any fish to be domesticated, were first kept by the Chinese over 2,000 years ago. Koi (the word means “carp” in the Japanese language) originated in the Black Sea area and arrived in Japan as a food source. They were first bred for domestic traits in Nigata, in northeastern Japan, in the 1820’s.

Ichthyologists discover new facts about fish on a near-daily basis. You can read articles about their findings at:
http://sciencedailey.com/

Thanks Frank,

Until Next Time,

Dave