This dynamic app contains spatial information on the distributions of Dungeness crab fishery revenue, predicted humpback, and predicted blue whale distributions from November 2009 to April 2019, relative to the seven RAMP zones. This tool is based on Samhouri et al. (2021) and Welch et al. (2023).
To allow for retrospective analysis on how enacting California Risk Assessment and Mitigation Program (RAMP) zone closures affects trade-offs between avoiding risk of whale entanglements in crab fishing gear and protecting crab fisheries revenue.
For example, if current ocean conditions are shaping up to resemble those in fall 2017-winter 2018, this app allows users to test how different zone closures affect trade-offs between avoided whale risk and protected fisheries revenue (Tab 1), find the optimal zone/s to close to maximize trade-offs (Tab 2), and maps distributions of whales and revenue (Tab 3) for the 2017-2018 season. This information can provide insights into current socio-ecological distributions and the types of closures that may maximize trade-offs under current ocean conditions.
Revenue - USD value of landings per grid cell using vessel monitoring system (VMS) data linked to California landings receipts registered to Dungeness crab (Samhouri et al., 2021).
Whale distributions - Modeled distributions for blue and humpback whales based on species distribution models (Abrahms et al., 2019; Samhouri et al., 2021).
Risk - The product of fishery effort and blue or humpback whale distribution.
RAMP zones - Fishing zone closures used by the Risk Assessment and Mitigation Program to support management of the Dungeness crab fishery in California.
Fisheries displacement - The % of fisheries effort in closed zones is redistributed proportionally to observed fisheries effort in open pixels (e.g. pixels that had higher observed effort received more redistributed effort, see Samhouri et al. (2021).
Redacted information due to MSA confidentiality restrictions - Pixels with VMS data from fewer than three vessels were removed from the fisheries revenue map in Tab 3.
Tab 1: Test zone closures
Allows for the exploration of trade-offs from user-defined zone closures. Explore % of fisheries revenue protected and % whale risk avoided under different management scenarios. To test a management scenario, select which zone/s and time-period to close, how much fisheries effort to displace, and then click Calculate Tradeoffs. For the selected inputs, returns:
- Tradeoffs: the % of total revenue protected and whale risk avoided, absolute values for revenue protected and whale risk avoided.
- Monthly values within closed zones for revenue and whale risk.
Tab 2: Find optimal zone/s to close
Allows the user to find the best zones to close to maximize trade-offs. Find the optimal zones to close to one of three possible objectives: 1. By closest to optimal (result will be as close to 100% of revenue protected and 100% of whale risk avoided as possible); 2. By minimum revenue protected (result maximize avoided whale risk while protecting at minimum the user-defined revenue); 3. By minimum whale risk avoided (result will maximize protected revenue while avoiding at minimum the user-defined whale risk). For the selected inputs, returns:
- Tradeoffs: the % of total revenue protected and whale risk avoided, absolute values for revenue protected and whale risk avoided.
- Equally well performing scenarios that protect the same % of total revenue and avoid the same % of whale risk avoided.
Tab 3: View maps
View the distributions of fisheries revenue ($), blue and humpback whales (normalized between 0-1), and entanglement risk (a function of fishing vessel and whale distribution) for a user-defined month.