They capitalized on the natural resources by using the salt to cure fish, which they exported to their home country.
( They ( ( ( capitalized ( on ( the ( natural resources ) ) ) ) ( by ( using ( the ( salt ( to ( cure ( ( fish , ) ( which ( they ( exported ( to ( their ( home country ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD capitalized) (PP (IN on) (NP (DT the) (JJ natural) (NNS resources))) (PP (IN by) (S (VP (VBG using) (NP (DT the) (NN salt) (S (VP (TO to) (VP (VB cure) (NP (NP (NN fish)) (, ,) (SBAR (WHNP (WDT which)) (S (NP (PRP they)) (VP (VBD exported) (PP (TO to) (NP (PRP$ their) (NN home) (NN country))))))))))))))) (. .)))
They used salt to cure fish and sent it back home. 
( They ( ( ( ( ( used salt ) ( to ( cure fish ) ) ) and ) ( ( sent it ) ( back home ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VP (VBD used) (NP (NN salt)) (S (VP (TO to) (VP (VB cure) (NP (NN fish)))))) (CC and) (VP (VBD sent) (NP (PRP it)) (ADVP (RB back) (NN home)))) (. .)))