Effects of electrofishing removal on the channel catfish, Ictalurus punctatus, population in the San Juan River, New Mexico
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The introduction of non-native species has been tied to the decline of native species in many areas around the world. The impacts of non-native introductions on native fisheries have prompted the establishment of non-native removal programs to suppress these populations of non-native species. The San Juan River Recovery and Implementation Program was established to mitigate the effects of the non-native channel catfish (Ictalurus punctatus (Rafinesque)) on native endangered fishes in the San Juan River. Although the recovery program has removed more than 136,000 channel catfish in the last ten years, a resurgence in endangered fishes has not been observed in the San Juan River. The recovery program personnel determined that population structure and maturation data were needed to establish what the current channel catfish population in the San Juan River looked like. This study evaluated the population structure and reproductive structure of the removed channel catfish population in the San Juan River 2011. The objectives of this study were to establish an age length key and to determine the age at maturation for channel catfish in the San Juan River. Channel catfish were collected between the months of June and August 2011 using raft mounted electrofishing gear. Length and weight were recorded for each fish removed, and samples of pectoral spines and gonads were collected to determine age and maturation. Data suggest that when compared with populations of channel catfish exhibiting normal growth the San Juan River channel catfish population is growing faster and is larger at a given age. However, data also suggest that only a small number of channel catfish are collected reproductively active, and all of these fish are > 400 mm total length (TL). Data also suggest that when compared with other channel catfish populations the San Juan River population is mature at a greater age. Based on these data the channel catfish population in the San Juan River may be compensating for removals and decreased densities by growing more quickly. These data indicate that the removal and recovery program should target large fecund adults to reduce recruitment and suppress the non-native population of channel catfish.