That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.

Two articles addressing fresh water and marine fish conservation issues were published this week:

Oriental Weatherfishes in Spain

According to an article in Biological Invasions, the Oriental Weatherfish (native to eastern Russia, south and Southeast Asia) is now well established throughout Spain’s Ebro River delta, and has a foothold in the Onyar River as well. This is of particular concern because over 80% of the Iberian Peninsula’s freshwater fishes are already considered to be threatened, with introduced species outnumbering natives in most rivers.

Last year, studies of the eel fishery in the Ebro River revealed that 8.2 tons of non-target fish, representing 17 species, are captured along with each ton of eels (elvers) harvested.  Approximately 40% of these fish perish before they can be released.

Fishes of the Coral Triangle

Reef fishes are becoming increasingly popular on restaurant menus throughout Southeast Asia and mainland China.  Particularly hard hit are species native to the waters bordered by Malaysia, Indonesia, Papua New Guinea, the Philippines, East Timor and the Solomon Islands.  Known as the “Coral Triangle”, this region is home to 75% of all known species of coral.

According to a recent Conservation Biology article, spawning aggregations of local species have declined by 79% in recent years, largely due to over-fishing.  Groupers, 26 species of which are endangered, have suffered the most.  Conservation efforts are complicated by the large number of countries having interests in these waters.

Thanks, until next time, Frank Indiviglio.

For further information on the natural history and captive care of weatherfishes, please see:

http://blogs.thatpetplace.com/thatfishblog/2008/05/22/fish-for-the-cold-water-aquarium-%e2%80%93-the-oriental-weatherfish-misgurnus-anguillicaudatus-the-european-weatherfish-misgurnus-fossilis/

In the wild, weatherfishes spend a good deal of time buried in the substrate, with just their heads protruding. In contrast to most other burrowing fish, they become quite bold in the aquarium and quickly abandon their secretive ways. Still, a soft substrate is appreciated, and it is quite amusing to see them burst forth from the sand when they detect food. I suggest Aqua Terra sand. If you do use gravel, be sure it is a smooth variety, such as walnut gravel, so that the delicate skin will not be damaged.

Always hungry, weatherfishes spend a good deal of time foraging – and in doing so are likely to uproot growing plants. However, well-rooted aquarium plants should be included in the aquarium when possible, as the fish seem to favor resting among plant leaves and stems.

Although weatherfishes get along quite handily without much aeration, their tank should be have a good aquarium filter as these ravenous feeders produce a good deal of waste.

Temperature and Other Water Parameters
The European species is adapted to cool and cold climates, and does best if water temperatures are kept below 75F. Oriental weatherfishes are far more adaptable, and inhabit areas where the water temperatures range from 36 -86F. They become inactive when temperatures dip below 50F or so, and are best kept at 66-75F.

Weatherfishes are undemanding as regards pH and water hardness, but do best at a pH of 7 or slightly below and in soft water.

Feeding
Weatherfish do a fine job of consuming food missed by tank-mates. Armed with sensory barbels, they miss little and will even root below gravel and rocks for food trapped there. However, they have quite large appetites and should by no means be expected to get by on leftovers.

Both species do best when offered a variety of foods. Although primarily carnivorous, weatherfishes should also be given food preparations that contain some plant material, such as flake fish food and Tetra tablets. A variety of freeze dried fish food, such as bloodworms and krill, should also be offered.

Free-living weatherfishes feed largely upon insects and other invertebrates, and captives do best when given ample live food. They particularly favor crushed crickets, blackworms, brine shrimp and small earthworms, and will take bits of fish and wild-caught insects as well. I have kept a number of individuals of both species for decades (see below) and attribute some of my success to a diet high in a variety of live foods.

Social Grouping/Compatible Species
Weatherfishes seem quite social by nature, and often rest in physical contact with others of their kind. You may even see them “exploring” one another with their barbels. They are sturdy enough to be kept with fairly large fish, and do not bother smaller animals (however, they will consume fish eggs and, possibly, fry). I have successfully kept them with fairly aggressive animals such as American eels and African clawed frogs without incident.

Captive Longevity
An Oriental weatherfish in my collection lived for 21 years. Longevities of 10-15 years are regularly reported.

Breeding
Breeding can be induced in both species by gradually lowering the water temperature to 60-65F while simultaneously dropping the water level to ½ the usual level and shortening the light cycle to 8 hours. After 2-4 weeks (longer periods may be required by fish from certain populations), water of approximately 10F warmer than ambient should be added to raise the water level back to normal. The temperature should be maintained at 72-75F and the light cycle increased to 14 hours.

The greenish eggs are attached to plants and the substrate following a “mating dance” of sorts. The males, distinguishable by their slightly larger and triangularly shaped pectoral fins, fertilize the eggs externally. It is best to remove the eggs (or adults) for hatching, which occurs in 3-5 days. The fry readily accept Daphnia, newly hatched brine shrimp prod, chopped blackworms and other live foods, and there are reports that they will take flake fish food and finely chopped frozen bloodworms as well.

Miscellaneous
Weatherfishes are exceptionally responsive to food and take readily to hand feeding – they will even wiggle onto a palm held partially out of water for a favored treat. To encourage hand feeding, try using freeze-dried or fresh prawn.

As mentioned in Part I of this article, I have encountered Oriental weatherfishes of 12-13 inches in food markets in two of NYC’s Chinese communities. The fish I found were in poor shape, but you may wish to keep an eye out for others in food markets – those I saw were much larger than pet trade animals, and would have made spectacular additions to any collection.

Please be aware that weatherfishes, like eels, catfishes and other scale-less species, are sensitive to many fish medications. Be sure to read the label carefully, or write in to this blog for more information.

I look forward to hearing about your experiences with weatherfishes, and to addressing any questions you might have. Thanks. Until next time, Frank.

Further information about weatherfishes is available at:
http://www.fishbase.com/Summary/speciesSummary.php?ID=3016&genusname=Misgurnus&speciesname=anguillicaudatus

Overview
Weatherfishes do not receive nearly the attention they deserve from aquarists, often being purchased as “curiosities” or “scavengers”. This is unfortunate, as they are among the most interesting of all fishes, and are very hardy as well. Their inquisitive dispositions and readiness to feed from the hand can only be described as “charming”. In part 2 of this article we will learn more about how to keep and enjoy them in the aquarium.

Two species are regularly available – the European weatherfish and the Oriental weatherfish (also sold as the dojo loach or Japanese weatherfish). The Oriental weatherfish is more commonly seen in the pet trade in the USA.

Physical Description
Weatherfishes have elongated, eel-like bodies with 5 pairs of fleshy barbels (sensory organs) surrounding the mouth. Their color ranges from metallic and golden tan through various shades of brown. The European species is striped, while the Oriental weatherfish is largely spotted, but both exhibit a mixed pattern of these markings. The Oriental weatherfish is also available in gold and albino color morphs.

Each can reach 12 inches in length, but rarely exceed 8 inches in the aquarium. I at first thought this was be due to a poor diet, i.e. their having to subsist upon “leftovers”. However, a number of individuals of both species that I have kept (including an Oriental weatherfish that reached age 21) also topped out at that length, despite being fed a diet rich in insects, snails and aquatic worms. I did see animals of 12-13 inches in a food market in a Chinese community in NYC. I was told that they had been imported from Hong Kong, but the store owner did not know whether they had been wild-caught or farm-raised. Perhaps, as with other fish species, local populations or races vary greatly in size.

Weatherfishes are classified as loaches, in the family Cobitidae. Many of the 118 species in this family of fresh water fishes, including the coolie loach, clown loach, yo-yo loach and hill stream loach, are popular with aquarists.

Range and Habitat
Both species have a huge range and are equally at home in many types of waterways. The European weatherfish favors rivers, streams and lakes, but is able to tolerate farm ponds and other less-than-ideal habitats as well. The Asian species is found in every type of fresh water environment imaginable. Due to its ability to take oxygen from the air, it is found in stagnant waters and does quite well in swamps, ditches and rice fields.

The Oriental weatherfish occurs from southern Russia south through India and China to Vietnam, Korea and Japan and has been introduced to Australia, Germany, the Philippines, Palau and the USA (Hawaii, California, Idaho, Indiana, Illinois). Much to the horror of loach fanciers, it is used as fish bait in some places, a fact that may in part account for the widespread feral populations. Detailed fieldwork has not been carried out with regard to introduced populations. However, as ravenous predators of invertebrates and fish eggs, it is suspected that they are negatively affecting local species. For this reason, weatherfishes are illegal to possess in Australia and England.

The European species occupies most of Europe except for Great Britain, Ireland, Scandinavia and Greece. Introduced populations have been found in Italy, Spain, Croatia and the USA (Great Lakes region and possibly elsewhere).

Diet
Both species feed largely upon insects, snails, worms and terrestrial invertebrates that fall into the water. They will also feed upon carrion and likely take fish eggs and fry as well.

Reproduction
Rising temperatures and water levels stimulate breeding in both species. Pairs perform “mating dance” of sorts during which the male wraps himself about the female and fertilizes the eggs as they are laid. The eggs are greenish in color and attach to plants and the substrate. No parental care is provided.

Miscellaneous
The weatherfish owes its common name to its unique habit of becoming very active just before a storm. This activity apparently is caused by the effects of barometric pressure (change in air pressure) upon the swim bladder. Weatherfish are among the earliest fish species to have been maintained in captivity – farmers in medieval Europe kept them for their weather predicting abilities, and in Japan they were much valued for their habit of swimming to the water’s surface prior to earthquakes.

Weatherfishes can breathe atmospheric oxygen, a facility that allows them to survive in swamps, rice fields and other habitats unsuitable for many fishes. Interestingly, they have evolved a respiratory system that is quite different than that employed by the “labyrinth breathers” (gouramis), lungfishes and other species that utilize air-borne oxygen. When breathing from the water’s surface, weatherfishes gulp air, absorb its oxygen within the gut and expel the excess via the anus.

During droughts, both species aestivate by burrowing into the mud, where they survive without water for quite long periods. Weatherfishes living in temperate areas spend the cooler seasons below the mud as well.

Please write in with your questions. I am very interested in hearing from you concerning the sizes your weatherfishes have reached, or if you have observed large individuals in food markets. Thanks, Frank.

An interesting article about introduced populations of the Oriental weatherfish (here and abroad) is posted at:http://www.thefreelibrary.com/New+records+for+the+alien+oriental+weatherfish,+Misgurnus…-a0162455040