At-Vessel and Post-Release Mortality

Fisheries bycatch mortality includes observable (at-vessel) and cryptic mortality, with post-release mortality a component of the latter. Research in this category examines factors affecting at-vessel mortality (AVM) and post-release mortality (PRM), to both improve the accuracy of bycatch estimates (which feed into population status assessments and hence management measures), and to develop techniques and strategies to reduce capture mortality.

Factors affecting bycatch mortality include operational (e.g., gear type, soak time, leader type, fishing depth, handling practices), environmental (e.g., sea surface temperatures, season, weather) and biological (e.g., species, sex, size) variables. Tagging studies are often used to investigate PRM.


  • At-vessel mortality is synonymous with at-haulback mortality, or hooking mortality.
  • Post-release mortality is synonymous with post-release survival.

Search Tip

  • Use 'cryptic mortality' in the 'References' keyword filter to find references specific to this topic. Leave the 'management category' filter open.


  1. Dapp DR, Huveneers C, Walker TI, et al (2016) Moving from Measuring to Predicting Bycatch Mortality: Predicting the Capture Condition of a Longline-Caught Pelagic Shark. Front Mar Sci 2:126. doi: 10.3389/fmars.2015.00126
  2. Ellis JR, McCully Phillips SR, Poisson F (2017) A review of capture and post-release mortality of elasmobranchs [IOTC-WPEB-IP-INF03]. J Fish Biol 90:653–722.
  3. Gilman E, Suuronen P, Hall M, Kennelly S (2013) Causes and methods to estimate cryptic sources of fishing mortality. Journal of Fish Biology 83:766–803.
  4. Williard A, Parga M, Sagarminaga R, Swimmer Y (2015) Physiological ramifications for loggerhead turtles captured in pelagic longlines. Biology Letters 11:20150607. doi: 10.1098/rsbl.2015.0607