Parental nutrient contribution of two closely related, sympatric pipefish species was investigated following exposure to mid-range environmental concentrations of the polychlorinated biphenyl (PCB) mixture Aroclor 1254 (mean ±s.e. = 52·89 ± 2·12 μg l−1). This study tested the hypothesis that differential nutrient supplementation during development predicts interspecific sensitivity to environmental stressors. Specifically, paternal PCB exposure was predicted to affect Syngnathus fuscus development because embryos depend on paternally derived nutrient sources in the brood pouch. Conversely, changes in Syngnathus floridae egg production were expected following maternal PCB treatment as a nurse-egg system generates the nutrient-rich pouch fluid. Lipid concentrations in adult blood plasma were significantly elevated following Aroclor 1254 treatment in S. floridae gravid females and post-brooding S. fuscus males (P < 0·001) which suggested mobilization from body tissues in response to metabolic demands. Aroclor 1254 treatment also resulted in decreased protein concentrations in S. fuscus pouch fluid (P < 0·05). These changes were not translated into significant exposure-related effects in the nutrient reserves of eggs and fry or fry size. Overall S. fuscus demonstrated a general sensitivity to disturbances from laboratory exposure conditions. Whereas a previous investigation of field-collected pipefishes showed comparable interspecific pouch fluid and fry nutrient concentrations and egg size, here, nutrient levels and egg diameter decreased in both laboratory-mated control and PCB-exposed S. fuscus. This study demonstrates the potential physiological effects of PCB exposure on parental nutrient allocation in syngnathids and the general sensitivity of S. fuscus to environmental disturbances.