Captive Care Notes: Slender Chubs (Erimystax, Family Cyprinidae)
The rarity of the Slender Chub (Erimystax cahni) has prompted Conservation Fisheries, Inc. (CFI) to develop techniques for its captive propagation. Lacking specimens of this chub, CFI opted to use two closely related and non-protected species, Blotched Chub (E. insignis) and Streamline Chub (E. dissimilis), as surrogates. Sixteen specimens of the former and 19 of the latter were placed in a 100-gallon aquarium equipped with internal and external pumps to provide water movement. Photoperiod, temperature, and feeding were similar to that for Spotfin Chub (Erimonax monachus), and were all increased to simulate spring-like conditions in the wild. Initially, the aquarium was furnished with relatively fine substrate (2-3 mm), several slab-rocks, and nylon spawning mops. However, spawning did not occur until after a pile of coarse gravel was placed in the main current of the aquarium. Both species spawned in and around the gravel pile. Eggs were apparently laid in relatively small numbers since usually less than 35 eggs were found at a time.
Eggs were siphoned from the gravel and placed into incubation trays. Hatching occurred four days later. The somewhat S-shaped larvae remained motionless at the bottom of the trays but would attempt to swim down into the substrate when disturbed. Within two days of hatching, the larvae began to swim up into the water column, but would drift back to the bottom when not actively swimming. At this point the larvae were transferred to a 20-gallon aquarium, where they began feeding in Artemia nauplii approximately one week after hatching. The larvae behave much like the larvae of spotfin chub, pretty much staying near the bottom. (This suggests the need for clean substrate to insure maximum larval survival in nature.)