Confirmation of catfish, Ictalurus punctatus (Rafinesque), mortality from Microcystis toxins

Abstract

Unexplained deaths of pond‐grown catfish have occurred for many years. At least some of these mortalities could be from cyanobacteria toxins ingested during feeding on floating diets or passively assimilated through gills during breathing. Recently we were able to document algal production and subsequent ingestion of these toxicants by catfish during a mortality event. The causative organism, Microcystis aeruginosa, was the dominant species within the phytoplankton community during the cooler autumn‐winter season. Pond conditions included a drop in water temperature by c. 5 °C during the 10 days preceding the fish mortalities. Microcystin‐LR, a hepatotoxin produced by Microcystis, was detected in water samples and in catfish liver tissue. Fish exposed to pond water containing this toxic bloom were killed within 24 h. Necropsy of fish revealed congested liver and spleen tissues. The combination of clinical signs, detection of microcystin LR in water and in liver, and death of fish exposed to pond water supports the diagnosis of microcystin toxicosis. More research is needed to identify specific environmental conditions initiating toxin production to model and predict occurrence of these toxic algal blooms.

Renal accumulation and effects of intraperitoneal injection of extracted microcystins in omnivorous crucian carp (Carassius auratus)

“…There have been many studies to document animal deaths or animal-poisoning episodes associated with the occurrence of toxic cyanobacterial blooms (Dawson, 1998;Zimba et al, 2001;Jewel et al, 2003;Qiu et al, 2007). Microcystins (MCs) are a family of cyclic hepatopeptide hepatotoxins produced by several cyanobacterial species.…”

Response and recovery of hybrid sturgeon from subchronic oral administration of cyanobacteria

“…MCs have resulted in illness and mortality of domestic animals, and fish, even a potential threat to human health (Rodger et al, 1994;Chorus and Bartram, 1999;Zimba et al, 2001;Jewel et al, 2003). Malbrouck and Kestemont (2006) have summarized in detail the toxic effects of MCs on various fish species, including salmoniformes, siluriformes, cypriniformes, as well as perciformes.…”

Dynamics of microcystins-LR and -RR in the phytoplanktivorous silver carp in a sub-chronic toxicity experiment

“…Many experimental studies have been conducted to document the toxicity of microcystin exposure through gastrointestinal or blood circular systems on (1) omnivores (animals, plant and detritus-eating) fish such as common carp (Rabergh et al, 1991;Li et al, 2001;Wu et al, 2002), and gold fish (Xu et al, 1998), (2) invertebrateeating carnivores such as Atlantic salmon (Williams et al, 1995(Williams et al, , 1997, rainbow trout (Sahin et al, 1996;Bury et al, 1996Bury et al, , 1997Tencalla and Dietrich, 1997;, and channel catfish (Zimba et al, 2001), (3) piscivores such as brown trout (Bury et al, 1997), Northern snakehead (Chen et al, 1995), and (4) macrophytes-eating herbivores such as grass carp (Chen et al, 1995;Zhang et al, 1996). However, all these studies were limited to acute toxic experiments, and they were based on either oral gavaging, or intraperitoneal injection, or administration via the dorsal aorta of the toxins, which cannot reflect the uptake route under natural environments.…”