add metadata to vignette

vignettes/nwfscDiscard.Rmd

@@ -224,6 +224,35 @@ combine_cs_discards(
 )
 ```
 
+## Metadata
+
+Description of data products:
+
+- Confidentiality Checks:
+
+  - confidentiality_catch_share.csv: The number of observed vessels, trips, hauls, and observations on non-catch and catch-share vessels of selected species given the request data stratification by area and gear type. To meet confidentiality a total of three or more vessels must be observed by stratification and year.
+
+  - confidentiality_em_catch_share.csv: The number of observed vessels, trips, hauls, and observations on vessels using electronic monitoring (EM) of selected species given the request data stratification by area and gear type. To meet confidentiality a total of three or more vessels must be observed by stratification and year. The confidentiality check for EM vessels is separate from the previous confidentiality check since the EM data are in a separate data file given the unique nature of the data. The EM program began in 2015 and is limited to catch-share vessels with participation increasing in recent years. 
+
+- Biological Data:
+
+  - biological_discard_lengths.csv and biological_discard_ages.csv: The length/age observations of discarded fish formatted based on requested stratification, data bin structure, and sex. Only select species include sex-specific data within WCGOP. Data are formatted for SS3. 
+
+  - discard_mean_body_weights.csv: The mean body weight in kg of discarded fish. Only years with 30 or more observations by stratification are provided. Data are formatted for SS3. 
+
+- Discard Rates:
+
+  - discard_rates_catch_share.csv: The observed discard totals and rates for catch-share vessels. The catch-share fishery has full observer coverage, hence data are considered a census and no measure of uncertainty are provided. 
+
+  - discard_rates_em_catch_share.csv:  The observed discard totals and rates for catch-share vessels using EM. These data are considered a census and no measure of uncertainty are provided. 
+
+  - discard_rates_combined_catch_share.csv: The combined discard totals between the catch-share vessels with onboard observers and  those using EM. Analysts should use this file when determining how to combine discard rates between catch-share and non-catch share vessels for use in stock assessment.
+
+  - discard_rates_noncatch_share.csv: The observed discard totals and rates for non-catch share vessels. These data are bootstrapped to estimate median discard rates and standard deviation for use in assessment.
+
+  - **The discards rates bewteen catch share and non-catch share vessels should be combined together to create a single discard rate by year and fleet for use within SS3.**  How to combine these discard rates should be carefully considered by analysts depending upon the magnitude of total landings (not just observed landings) between catch share and non-catch share vessels. 
+
+