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Tag Archives: Aquarium Fish

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Decline of Apex Predators – Why Shark Finning Needs to Stop

Shark Fin SoupHello, Cory here. Almost every day you can find some piece of news involving sharks, and in many cases, the news is another instance of someone, somewhere discovering mutilated shark carcasses or that a commercial fishing boat has been found throwing finless carcasses overboard. Just the idea of shark finning is terrible, I’m not sure how anyone can support and/or participate in the shark fin trade. Shark finning has been banned in many countries such as the US, but remains a problem in European and Asian countries. Despite the concern over shark populations and environmental impacts, shark finning continues, even growing from year to year in popularity, all to cater to a taste for an expensive bowl of soupRead More »

The Weather and Fish Availability

Welcome back Cory Shank with an article on aquarium fish availability.

Throughout the year, the availability of certain aquarium fish and invertebrates can change for what seems to be no reason at all. It may be for a few days to a week or even a few weeks extending into months. There are many reasons for absence of your favorite aquarium resident, but the one most overlooked is the weather.

One must remember that almost every aquarium inhabitant has begun their journey from the rivers, lakes, and oceans from where they reside. Now if the fish or invertebrate is either tank raised or tank bred, then obviously they have not traveled that far, but for the most part everything is collected from the wild. The weather is quite variable, especially in the tropics, season to season. This is where most of the marine organisms are collected. The largest interruptions from the Caribbean to the Indo-Pacfic regions are during the hurricane season. The Caribbean tends to be more vulnerable to tropical systems than the Indo-Pacific regions, mainly because of the size difference.

Blue Leg Hermits sometimes become scarce due to weatherHurricanes, tropical storms, and even tropical depressions and waves cause an increase in wind, generating larger ocean swells, which can wreak havoc in shallow collection areas. Obviously during a hurricane divers can not enter the water and collect fish, but one storm can delay collection for up to a week or even longer. As seen with Hurricane Ike, 2 days prior to the storm, there were waves and tides above the norm, nearly a thousand miles from the storm, affecting the entire Gulf of Mexico and parts of the Caribbean. After the storm passes, collection depends on how fast the water clarity increases, this can take a few more days to happen. Looking at this situation, the collection for one area can be shut down for a full week. This increases the demand for certain organisms, making the availability for the following week extremely high, which leads to a less than healthy fill rate for orders for the orders following a storm. The Caribbean has been highly vulnerable this year, with a few storms passing through major collection areas of Scarlet Reef and Blue Leg Hermit Crabs, along with Royal Grammas, and Peppermint Shrimp.

Hurricanes are not the only culprit: excessively warm or cold water can affect availability. Organisms will move from shallow regions to deeper zones to escape a time of warmer water. This can also be a seasonal migration, affecting availability for a longer term. El Nino and La Nina can lead to big changes in global water temperatures. In such extreme events such as the 1997-98 El Nino event, populations can be severely impacted. Responsible marine fish and invertebrate collectors will either halt or decrease collection significantly in order to help the population rebound.

Royal Grammas can be hard to come by during harsh weatherWeather can also play a role after the fish have been collected. After collection, the organisms will be sent to the wholesaler’s facility. In order for the organisms to arrive safe and in good health at your local pet store, the weather along the route must be taken into consideration. The time of transport relies heavily on how the fast the airlines can get the fish to their final destination. A heat wave can destroy an entire shipment if it were to be delayed by even a few hours. The same goes for extremely cold weather in parts of the country. The shipment, if delayed, could become frozen if the heat packs fail or run out.

So the next time you can’t find your favorite fish at the store, think about where it is coming from and what the weather is like in its hometown!

Thanks Cory,

Until Next Time,


Blind Cave Fish: Their Discovery, Initial Collection and Care – Part 2

Blind Cave Fish

Click here to read the first part of Blind Cave Fish
Blind cave fish navigate entirely through the use of the lateral line – a system of sensory organs possessed by all fish but, it seems, very highly developed in this species. The movement of water (caused by currents or the fishes’ own swimming) bouncing off objects is sensed and used to guide the fish in their travels. I am tempted to compare the process to echo-location in bats, or the use of electricity by the elephant nose fish, Gnathonemus petersi, but it is, of course, quite distinct. If you have an opportunity, observe how well cave fish can move about – in an exhibit at the NY Aquarium they speed through a series of glass barriers unerringly. Individuals introduced to new exhibits may “crash” on occasion, so there may be some learning involved as well.

They are also amazingly adept at locating food – a school I kept at the Prospect Park Zoo in NYC hit food dropped on the water’s surface as quickly as do most sighted fish. In fact, blind cave fish do quite well in aquariums housing other fish species.

Recently (January, 2008) it was discovered that young blind cave fish can detect light via unique compounds in the brain’s pineal gland (the embryos begin to develop eyes, but these degenerate rapidly). This ability declines with age.

In contrast to most cave-adapted fish – which require cold, hard water if they are to thrive – blind cave fish are quite undemanding pets. In fact, they do best at 78-82 F, as their native waters are quite warm. If kept alone, slightly hard water should be provided, but they adapt easily to conditions suited to most community-type tropical fish. Despite a very specific natural diet (see above), blind cave fish remain healthy on almost any commercial fish food – I have successfully used a mix of omnivore flakes and pellets, along with frozen foods. They ravenously devour black worms, brine shrimp and such, and are especially fond of crushed crickets and other insects. Their reaction to insect food brings, at least to my mind, an image of feeding behavior in their native cave. At feeding time, they compete quite well with other fish and rarely require special attention.

Blind cave fish are placed within the order Charachiformes, an extremely diverse group of fishes containing well over 1,500 species, including tetras and the infamous piranha. I will write about piranhas in a future article, and will include photos of some that became “attached” to me while I was seining for knife fish in northern South America. Until then, please forward your comments and questions. Thank you. Until next time, Frank.

A fascinating account of the first expedition to collect blind cave fishes, including original drawings and photos, is given in Zoo Expeditions, by William Bridges (William Morrow & Co., 1945). Long out of print, this book is well worth searching for.

An interesting article on the evolution of eye regression in this fish is posted at:

Thanks Frank,

Until Next Time,

Uncommon Facts About Common Aquarium Fish

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:

Thanks Frank,

Until Next Time,


World’s Oldest Aquarium Fish Celebrates 75 Years

I just read this article and thought I’d pass it along to you. It’s about an Australian Lungfish named Grandad that’s lived in the John G. Shedd Aquarium for 75 years, making it the oldest aquarium fish in captivity. As That Pet Place is the World’s Largest Pet Store, we’ve gotta’ support these Guinness-worthy fish achievements. Now I have heard many a “fish tale” about certain species living for years in various conditions, obviously pond koi come to mind, but I’d love to hear any fish records. Take a look for yourself. This article and picture were originally posted by the Daily Herald in Chicago. The image is taken from there. “The Oldest Aquarium Fish in the World Celebrates 75 Years”

Until Next Time,