Jan Jeffrey Hoover and K. Jack Killgore
Fish Ecology Team, Environmental Laboratory
United States Army Engineer Research and Development Center
During the past 17 years of sampling the Lower Mississippi River, the US Army Engineer Research and Development Center (ERDC) Fish Ecology Team has collected more than 2,050 flathead catfish, 9,300 channel catfish, and 22,230 blue catfish – making that species the most common of large bottom-dwelling fishes. Some variation in color exists, from darkly pigmented (melanistic) to snowy white (leucistic), but one variety of blue catfish is the rarest: the piebald blue. “Piebald” is a portmanteau of “magpie” (a black and white bird) and “bald” (for white patch or spot) and refers to a distinctive, but highly variable pattern of mottling in animals. Having the same size and shape as an ordinary blue catfish, piebald blues stand out because of their white skin marbled with prominent black and/or gray blotches. Catching one makes for a memorable experience. Only two have been collected by our team.
On 22 Feb 2002, we collected a piebald blue near Greenville, MS (Fig. 1). It was missing its right eye and the fish was almost entirely white with the exceptions of a black triangular patch behind the left pectoral fin and black highlights in all fins except the adipose. We maintained it overnight in our boat’s aerated live-well until we returned to ERDC but air temperatures plunged from 70 to 28 F which is stressful for temperate fish. The fish survived, however, and we set it up in a 1600-liter flume (flowing water aquarium). It was fed frozen shrimp, live earthworms, and live fathead minnows – which it ate sporadically. After three weeks, the black highlights began to enlarge and multiply. In early April, it was substantially more marked than it had been when caught – with black fins (including the adipose fin), black saddles on the back at the base of the fins, and black belly and lower sides. The fish appeared to be in good condition and exhibited no external signs of disease, but in late April began to act disoriented. It died on 23 Apr 2002 from unknown causes. At the time of its death, the fish was 422 mm in total length and weighed 605 g.
A decade later, on 27 Sep 2012, the team collected another piebald blue, this time near Vicksburg, MS (Fig. 2). This fish was in perfect condition, was slate gray dorsally, and white ventrally, with smatterings of gray in the caudal fin, and a few white spots on the head and back. It was captured in a hoop net during a field trip attended by biologists from USFWS, LMRCC, Tara Wildlife, and ERDC, and during which prominent conservationist Theodore Roosevelt IV toured the lower river, observing its underwater denizens (Fig. 3). The fish was retained for display at a public aquarium but unfortunately died in transit.
Explanations for the coloration of piebald blues will probably remain a mystery due to their extreme rarity. Whether this rarity is due to low occurrences, or to high predation from larger fish stimulated by their conspicuous appearance, is speculative. If, however, a piebald blue could be successfully transferred to an aquaculture facility, breeding experiments and DNA-analyses of parents and offspring could determine whether these fish are the result of unusual genetic phenomena or simple accidents of nature.
We recently learned of a third piebald blue captured during winter 2012 in the Lower Mississippi River by Don Henke and Jerry Brown, biologists with the Mississippi Department of Wildlife Fisheries and Parks. Like the other specimens, it was collected during field surveys. Like our own 2012 fish, it was predominantly white ventrally and gray dorsally, with an irregular pattern of pigmentation (Fig. 4). After being photographed, it was released back into the river where it may still be swimming today.