(S (S (BASENP (PRP It)) (VP (VBZ is) (VP (VBN suspected) (SBAR (S (NP (BASENP (DT the) (NN fish) (POS 's)) (NN aggression)) (VP (MD could) (VP (VB have) (VP (VBN been) (NP (BASENP (DT a) (NN result)) (PP (IN of) (BASENP (DT a) (JJ hormonal) (NN imbalance)))))))))))) (PERIOD .))