Good day, folks! It may finally be summer, but here in Portland we’ve been having rainstorms all week. While not good for walking about, these rainy days can be useful for fish hobbyists – the resulting drop in barometric pressure at the beginning of a storm, or even the smaller dip that occurs approximately every two days in our area, can be combined with a well-timed water change using cooler water. This simulation of a monsoon encourages many fish to flirt and breed in the home aquarium.

Speaking of monsoons, the rainy season has come to South America and with it we’ve lost access to many fish. Despite being out of season, though, we’ve gotten a fair number of Hatchetfish coming in these past few weeks, including some species we don’t see very often. They’re limited in stock, but it’s been so long since we’ve had any of these species that I felt it prudent to mention them.

The popular hatchetfish are members of the only family of fish known to use powered flight - achieved by beating its pectoral fins like a bird's wings.  The hatchet's incredibly strong pectoral muscles account for approximately 25% of its body weight, allowing a fish as small as the Marble Hatchet Fish (topping out at only an inch and a half) to fly for several yards before reentering the water.  In general, these fish prefer a temperature of 75°F to 82°F, a pH between 5.0 and 7.5, and a minimal hardness of between 0 and 10 degrees. 

We typically only seeCarnegiella marthae "Marthae Hatchet Fish" once or twice a year, and this year has thus far been no exception. These little hatchets grow to barely over an inch and show very intricate patterns of black over their translucent silver bodies. The fish’s ventral edge, from just behind their gill plate to the end of their caudal peduncle, is rimmed in a thin black line. Concentric broken black stripes follow the curve of the gill plate, echoing across the keep of the fish to the back of its body. The fish’s lateral line is colored with thin black and silver stripes and its face is adorned with rippling black stripes. Finally, lending to its common name of the Black Winged Hatchetfish, its pectoral fins are bisected by deep black stripes.

Gasteropelecus maculatus “Black Spotted Hatchet Fish” is seen even less often. This hatchet is much larger, often arriving at two or more inches in length and growing to nearly four inches as an adult. It has a deep silver body, again rimmed at the ventral edge in black, though not to the same extent as the Marthae, and shows a dark lateral line with bold black spotting above and below. Their faces are marked with black, especially around the lips and below the eye. The base of their dorsal fin is as well bordered in black. These big, beautiful fish are sure to make an impact in any moderate to large sized aquarium.

Gasteropelecus maculatus - Spotted Hatchet Fish

That’s all for this week; now it is time for us to don our rain coats and head home for the weekend. I’ll see you back here next week!

Jessica Supalla