The low temperatures that’s been holding the state of Florida in a firm grip this winter is causing troubles for tropical fish raised in outdoor ponds. Aquarium fish farmers report losing up to 50% of popular tropical species to the cold, and a severe guppy shortage has already emerged – boosted by the fact that Americans are more inclined to purchase guppies and other aquarium inhabitants during the winter season.

Roughly half of the tropical fish sold in the United States is raised in Florida, a state heavily dependant on its warm climate. The fist fish farmers showed up here as early as the 1930s when it was still possible to purchase cheap land around Miami, but nowadays a majority of the fish Florida farms is found in the lake-rich part of Florida located between Tampa and Orlando. Up until a few years ago, the number one cargo shipment out of Tampa International Airport was tropical fish.

Fish native to tropical parts of the world normally find it difficult to stay alive if the water temperature drops below 60 degrees F (15 degrees C) and even temperatures around 70 degrees F (20 degrees C) may have a detrimental effect on their immune system. It is therefore easy to imagine what happens if the air temperature suddenly drops below the freezing point – as it has done in Florida this winter.

And even in situations where the cold isn’t severe enough to instantly kill the fish it can send them into a sedentary state where they fail to hide from predators like hungry birds, especially if living in unplanted ponds offering few places to hide. Many fish eating birds have been forced to see their normal hunting grounds being sealed off by ice and fish farms struggling to keep the water temperature up constitute a highly appealing alternative when the hunger sets in.

In desperate attempts to save their fish from freezing to death or being eaten by predators, Florida farmers have been covering their ponds with plastic sheets and pumped in warm water. When the cold turned out to be more than just a short dip, those who could scrambled to get as many fish as possible indoors. Many farmers have been forced to prioritize older fish close to the size needed for shipping, leaving younger fry behind to die.

Farmers that have lost more than 50 percent of their fish are entitled to financial relief from the Department of Agriculture if they file a crop insurance claim.

Several types of commonly used fish egg disinfectants increase the risk of swim bladder disorder in fish, a new study from Israel reveals.

In an effort to prevent fungal growth, many fish breeders use various chemicals, such as methylene blue, hydrogen peroxide, acriflavine and chloramine-T to aquariums where eggs are kept. This practise is especially common among breeders who will not let the parents stay with eggs and fry. Many fish species carry out parental care and eggs from such species often depend on one or both parents gently fanning fresh water over them and manually removing any unfertilized eggs from the batch. Without such parental care, the eggs easily succumb to fungi unless the fish breeder adds some type of fungicide to the water.

The new Israeli study, which focused on Angelfish (Pterophyllum scalare), revealed that some of these chemicals may be responsible for a swim bladder disorder in developing fish. In fish suffering from this type of disorder, the swim bladder can not inflate properly and the fry fails to develop into a fully free-swimming adult. Among aquarists, such fish are commonly known as “belly sliders” due to their peculiar way of moving around the fish tank.

Methylene blue

Eggs hatched in the presence of 1, 2 and 5 ppm methylene blue exhibited significant increases in swim bladder non-inflation (11%, 9% and 33%, respectively; none in controls).

Time of exposure to methylene blue was a key factor. Exposure for up to 1 day post-hatch did not affect swim bladder non-inflation, but exposure from 2 days onwards significantly increased swim bladder non-inflation.

Hydrogen peroxide

Hydrogen peroxide at 250 ppm significantly increased swim bladder non-inflation (65% comparing to 27% in the control). Higher concentrations resulted in 100% mortality.

Acriflavin

Exposure to acriflavin at 2.25 ppm, but not 1.25 ppm, significantly increased swim bladder non-inflation (75% and 52% respectively; 20% in controls).

Chloramin-T

Chloramine-T did not significantly affect swim bladder non-inflation.

For more information, see the paper “C. Sanabriaa, A. Diamantb and D. Zilberga (2009) – Effects of commonly used disinfectants and temperature on swim bladder non-inflation in freshwater angelfish, Pterophyllum scalare (Lichtenstein)”. The paper has been published in the journal Aquaculture.

The Indian government’s Marine Products Export Development Authority (MPEDA) is now launching a breeding program for the threatened Red line torpedo barb (Puntius denisonii).

Torpedo barb – Picture by brookfish

Puntius denisonii, commonly known as Red line torpedo barb, Roseline shark, or Denison barb, is native to the fast-flowing hill streams and rivers in Kerala, at state located in the southern part of India. It is highly sought after in the aquarium trade.

After several years of research, the MPEDA has now managed to successfully breed Red line torpedo barb using two different techniques: one that relies on hormone treatment to trigger spawning and one where the natural breeding conditions of this barb is recreated in captivity.

MPEDA hopes to be starting commercial production shortly.

Picture by brookfish