Tensile strength and knot security of five suture materials exposed to natural summer conditions of a temperate lake.

Wild fish and other aquatic ectotherms are often subjected to procedures during field research that requires wound closure using sutures. A variety of absorbable sutures are available for such purposes, yet degradation processes are highly dependent on temperature and the environments in which wild ectotherms are released are almost always colder than the conditions that absorbable sutures are typically designed for (i.e., ~37 °C). Here, we tested the tensile strengths and knot securities of loops tied with five different absorbable suture materials (PDS-II, dyed coated Vicryl, undyed coated Vicryl, plain gut, and chromic gut) prior to and during submersion in a temperate lake over an 8-week period. The naturally derived collagen-based suture materials (i.e., plain gut and chromic gut) exhibited major decreases in tensile strength within 2 weeks of submersion but maintained relatively high knot security throughout the study period. The synthetic suture loops had poorer initial knot securities that increased following submersion and showed little to no evidence of degradation after 8 weeks. We discuss the implications of absorbable suture degradation, or lack thereof, for fish welfare considerations such as suture retention, wound healing, inflammation, and infection under natural conditions.