I have the following letter from MINAET (Costa Rican Ministry of Enviroment) regarding Cano Island. I have translated it and only included the relevant info here:
"Caño Island Biology reserve land side will be closed from the 17th February for a period f 3 months. This is to comply with sanitary improvements (I guess toilet facilities and septic tank) requested by the Ministry of Health in resolution R-ACOSA-D-041-2012.
We confirm the marine part will be open for activities like snorkeling, scuba and navigation and if you like you can disembark at San Pedrillo in Corcovado National Park."