Evaluation of Acrylic Esophageal Tubes and Pulsed Gastric Lavage for Sampling Stomach

Non-lethal methods for sampling stomach contents of fish may vary in efficacy by species. We compared the effectiveness of acrylic esophageal tubes (a method often used to retrieve stomach contents of Largemouth Bass Micropterus salmoides) and pulsed gastric lavage at removing the stomach contents of another piscivore, Butterfly Peacock Bass Cichla ocellaris. Peacock bass were electrofished, measured, weighed, and immediately subjected to one of the two treatments.  Percent of stomach content mass removed and associated stomach tissue damage were assessed using fish dissection of euthanized fish following non-lethal treatment techniques.  Pulsed gastric lavage removed greater percent stomach content mass (68.3 ± 6.1;  ± SE)  on average than acrylic esophageal tubes (31.7 ± 9.1%;  K-W Χ²=14.11, df=1, p<0.05). The use of acrylic esophageal tubes resulted in higher incidence of bruising, tearing, and puncture of the stomach wall compared to pulsed gastric lavage (Χ² = 10.17, df=3, p<0.05). The size of diet items likely influenced the effectiveness of pulsed gastric lavage, with larger items often remaining in the stomach. Based on these results, pulsed gastric lavage appears to be the preferred non-lethal technique for sampling the diet of Peacock Bass, but can be biased, especially when prey have relative large body size.