Economics, Feeding, and Population Structure of Natrix S. Sipedonin a Goldfish Hatchery

Abstract

Most commercial fish hatcheries regularly kill all water snakes encountered around the rearing ponds. It is claimed that the snakes do great economic damage to the fish crop although no quantitative data is available. Ozark Fisheries Inc., located in central Missouri, is the largest goldfish (Carassius auratus) rearing company in the world. To encourage the elimination of water snakes the corporation has, for years, paid a small bounty for every water snake killed by one of their workers. Bounty records are kept as part of the expense of running the hatchery. Natrix s. sipedon is the only water snake found at Ozark Fisheries so all snake bounties pertain to that species.This study was conducted to determine: 1.The economic impact of Natrix s. sipedon on the hatchery operation. 2.Feeding and growth of this species under the conditions of an essentially unlimited food supply. 3.The influence of continual persecution on the population structure of this water snake. DESCRIPTION OF THE STUDY AREA Ozark Fisheries Inc. is in southern CamdenCounty, Missouri, near the northern edge of the Ozark Plateau. Oak-hickory covered ridges are separated by flat stream valleys. The streams are fed by large springs and the hatchery ponds are located along these valleys.

Preliminary Examination of Cultured Fish Consumption by the Diamondback Water Snake Nerodia rhombifera

“…The high variability was not unexpected as the studies of the authors [1,2] found empty stomachs in 51% and 65%, respectively of snakes of this genus.…”

“…However, the finding that fishfeeding Northern and diamondback water snakes could account for up to 50% of the "black hole" losses indicates they are significant predators on fish farms where large density of smaller fishes (i.e., hatcheries, bait fish, and goldfish farms) are found. Even with control measures, the live-bearing ability at one year of age by Northern water snakes has led to constant numbers harvested, albeit at a smaller size, at a Missouri goldfish hatchery (Bauman and Mettes 1976). Other areas of the world may experience similar issues depending on the species of water snake found and culture system.…”

“…Aquaculture, and especially hatchery, facilities are one such environment. Published work on negative impacts in aquaculture farms cover the Northern water snake, N. s. sipedonin [1]. From examination of specimens at a private fish hatchery in Missouri, they assumed these snakes consumed fish every other week at 30% of the snake body weight.…”

“…We estimated that number to be up to 10% of the cultured fishes, primarily goldfish. No studies have been conducted on the impact of N. rhombifer, the diamondback water snake [1].…”

Dietary resource utilization patterns and head morphology among three sympatric watersnake species.

“…It has the largest range of any watersnake in North America (Gibbons and Dorcas 2004), stretching across portions of the Great Plains, the majority of the eastern United States, southeastern Ontario (Gibbons and Dorcas 2004) and southern Quebec (Ernst and Ernst 2003). It can be found almost in any freshwater habitat type (Ernst andErnst 2003, Gibbons andDorcas 2004), including fish hatcheries (Bauman and Metter 1975), streams (Cecala et al 2010), lakes of various sizes (Zelnick 1966, King 1993) and a variety of wetlands (Roe et al 2003). It also uses a variety of foraging strategies including active foraging, ambush and tongue-flick probing (Meyer 1992, Balent andAndreadis 1998).…”