Crustaceans often undergo periods of starvation, due to natural food shortage or physiological constraints. During these periods, several metabolic and behavioral changes can occur. This study evaluates how the brown shrimp Crangon crangon (Linnaeus, 1758) responds to prolonged deprivation of food in two seasons of the year, and how this species mobilizes its energetic reserves. Shrimps caught in June (summer) and October (autumn) 2010 in the Minho estuary (north of Portugal) were placed in individual cages in experimental aquaria and kept in starvation until the last shrimp died or was sacrificed (six shrimp per aquarium every week). The energetic content, total lipids and total protein, and the oxygen consumption rate were compared between seasons, sacrificed and naturally dead shrimp, and considering the weeks of starvation. Summer shrimp proved to be better prepared to endure starvation than those caught in autumn: they survived 2.5 times longer, had a higher Fulton condition factor, higher energy, and higher lipid and protein content at the beginning of the experiments. The percentage of total body protein decreased significantly in the first week, stabilized in the following to decrease again abruptly in the fifth week. The percentage of total lipids only started to decrease after four weeks. This suggests that (1) C. crangon probably uses protein as a first energetic resource, followed by carbohydrates and eventually lipids, though to a much lesser extent; and (2) after 4 wk of starvation, a critical point is reached when structural components may be mobilized to satisfy maintenance costs.