The comparison between the Discard- and Unobserved-mortality studies will evaluate differences in RAMPs from the same fishery, but for two different types of bycatch (discard and unobserved). There were additional differences between the studies. These include that crab for the Unobserved-mortality study were assessed less than 15 min after being landed on deck. The crab were in air only briefly and were in water for the remainder of that time. The time in water was intended to reduce air exposure, but may have inadvertently served as a recovery period. In contrast, crab from the Discard-mortality study were exposed to air for 90 min on average (range from 9 to 230 min) without time in water.
While overall mortality rates for the two studies are likely to differ given that the two types of bycatch experience different stressors and given that there are typically more mortalities for discards than for animals that escape fishing gear (Broadhurst et al., 2006), we hypothesized that the relationship between Score for Tanner crab bycaught in the Alaska bottom trawl fishery and probability of mortality would be the same regardless of the type of bycatch (discard vs. unobserved). The goals of this study were to test this hypothesis to determine the extent to which RAMP can be applied once created, to assess components of the RAMP approach to clarify the methodology, and to evaluate the requirements and limitations of RAMP. The more that is known about RAMP the more useful it will be as a tool for promoting sustainability in fisheries by reducing uncertainty associated with bycatch mortality.