High discard survival merits exemptions to European Union ban on fishery discards

Atlantic cod, NOAA

The introduction of the obligation to land all catches (eliminate discards) in the recent reform of the Common Fisheries Policy (CFP) represents a fundamental shift in the management approach to European Union fisheries from regulation of landings to regulation of catch. Research has shown that not all discards die. In some cases, the proportion of discarded fish that survive can be substantial, depending on the species, fishery and other technical, biological and environmental factors. If these surviving animals are discarded instead of landed, they can contribute to future stock recruitment.

Article 15 paragraph 4(b) of the CFP regulation allows for the possibility of exemptions from the landing obligation for species for which "scientific evidence demonstrates high survival rates". Taking the first element of this "scientific evidence"- it is important that managers have guidance on protocols and methodologies that should be followed in order to ensure the results of such experiments are scientifically robust. Presently there are no such internationally agreed guidelines. EWG 13-16 has provided guidance on best practice to undertake survival studies. In this regard EWG 13-16 has identified three methodologies for conducting survival experiments i.e. captive observation experiments, vitality/reflex assessments, and tagging/biotelemetry experiments.

Captive observation experiments involve holding animals that have been captured after exposure to fishery stressors. Holding can be in tanks or net pens while short-term survival is observed.  Holding periods typically range from 3-21 days until mortality associated with experimental fishery stressors has abated. Discard survival rates in specific fisheries conditions are then modeled using data from holding experiments. Davis (2002) reviewed an array of potential explanatory variables for discard survival, which can be classified into three broad categories: biological (e.g. species, size, age, physical condition, occurrence of injuries), environmental (e.g. changes in: temperature, depth, light conditions) and operational (e.g. fishing method, catch size & composition, handling practices on deck, time exposed to air). The complexity and interactions of explanatory variables for discard survival could present a problem to fisheries managers because instead of simply asking “Can we discard this species?” it may be necessary to ask “when, where, and under what conditions can we discard this species?” A potentially unlimited variety of fishery condition combinations would need to be modeled for determining discard survival.

Effects of fish size, fishing gear type, and temperature on sablefish mortality, NOAA

Tagging/biotelemetry experiments are similar to captive observation experiments in that animals are captured after exposure to fishery stressors. Then animals are tagged, released, and monitored for survival either by recapture or by biotelemetry.  Survival observations can be made over periods of weeks, months, and years. In addition to the complications of fishery stressor variable interactions, these experiments have the additional complications of including sources of mortality associated with predation and food and habitat availability that are independent of the effects of the initial capture stressors.    

Vitality/reflex assessments are real time in situ determinations of animal vitality and health.  The animal integrates the effects of fishery stressors and lives or dies according to it’s level of vitality impairment. Davis (2010) has shown that calculation of an index for reflex impairment (RAMP, reflex action mortality predictor) based on summing observations of several reflex actions is a robust, quantitative measure of animal vitality that can include the effects of fishery stressors on animal survival. When animals are exposed to fishery stressors and captured, as described above for captive observation experiments and tagging/biotelemetry experiments, they exhibit various degrees of stress and impairment of vitality which can be associated with mortality and survival.  Correlation of RAMP scores with mortality or survival levels observed in captive observation experiments or tagging/biotelemetry experiments makes RAMP a proxy for mortality or survival (Raby et al. 2012). Further RAMP validation can be made by testing with additional holding or tagging experiments in fisheries of interest.

RAMP curves for Atlantic cod, Humborstad et al. 2009

Once validated, RAMP assessments could be used to identify species in a fishery that may have the potential to survive discarding, and that merit an exemption to the Landings Obligation. Where a large majority of individuals of a particular species demonstrated consistently high RAMP scores, and there were very few examples of immediate mortality, this would indicate that species may warrant further investigation to demonstrate its potential for short & long term survival, post-discarding. Using this approach, a large number of species could be assessed (quickly & inexpensively), over a wide range of conditions and for a variety of boats (& discarding practices) throughout the fishery. 

At the same time, continued development of innovative fishing gears and fisher avoidance of high bycatch areas and times can help reduce capture of unwanted species. RAMP can be used to evaluate the survival of animals that are impacted by fishing gears and escape before landing on fishing vessels. The banning of discarding will make the evaluation of mortality rates for animals escaping from fishing gears especially important. "Out of sight and out of mind" will not be a viable strategy with regards to evaluating fishing mortality for gears engineered to enhance escape of bycatch species.