# Assessing biological reference points for geoduck clam fishery

## Description

Files 1.The "refpoints.m" file contains a script to be used with the MATLAB software. The script calculates the probabilities that the biomass of a marine sessile resource as Panopea globosa will reach four fishery management reference points while being exploited at a constant exploitation rate (Larios-Castro et al., 2023). 2.The file "PreviousYears.xlsx" is an example matrix of size 4x4 with fictitious data on the magnitude of biomass three or four years prior to reaching the values defined as reference points (65%, 50%, 40%, and 30% with respect to virgin biomass). This array is necessary for the "refpoints.m" function to work. Use 1. The "refpoints" function creates four excel (.xls) files (Management Threshold Point, 0.65; Target Reference Point, 0.5; Limit Reference Point 0.4; and Depleted, 0.3), each containing a matrix of the calculated probabilities of reaching a fishery management reference point as the stock biomass is exploited and decreases. The columns of the matrix of each file correspond to 1. the Bt/Bv values. 2 - 7 correspond to the probabilities obtained considering six different standard deviations, the optimal value, a decrease and four increments with respect to the optimal value (sigmas = -10%, 0% +5%, +10%, +20%, +30 %). Additionally, the probability values calculated for each reference point will appear in the command window from the MATLAB interface. 2. The "refpoints" function needs an array in a file with a ".xlsx" extension previously constructed by the user (for example, PreviousYears.xlsx). This matrix should contain the Bt/Bv values for the three or four years prior to the reference point. The function will ask to select the .xlsx file manually, so you will have to save a copy in the "Current Folder" from the MATLAB interface along with the function file "refpoints.m". 3. "Ref" is a necessary vector of the four values corresponding to the four reference points. It must be previously defined by the user, for example: Ref = [0.65 0.5 0. 4 0.3]. With this option you can change the reference point values if necessary. 4. The "refpoints" function returns the values derived from the different standard deviations (sigmas) obtained from the "previous years" matrix. Bibliography: Larios-Castro, E., Morales-Bojórquez, E., Peláez, S. S. G., Díaz-Uribe, J. G., Luquin-Covarrubias, M. A., & Villalobos, H. (2023). An enhancement in the management practices of geoduck clam Panopea globosa: The estimation of reference points in the short and long term. Ocean & Coastal Management, 243, 106755.