Energetics of swimming to shore in the puerulus stage of a spiny lobster: Can a postlarval lobster afford the cost of crossing the continental shelf?

Lay Abstract In their nonfeeding postlarval stage, known as puerulus, spiny lobsters migrate tens of kilometers across the continental shelf to settle in coastal waters. A mathematical model is described that analyzes hydrodynamic forces during swimming in the puerulus of the New Zealand spiny lobster, and this model is used to estimate the metabolic cost of this migration. The cost of sustained swimming is compared with observed internal metabolic energy reserves (principally in the form of lipid) for pueruli collected 20 km off the east coast of New Zealand. Sustained swimming at speeds exceeding 15 cm s − 1 will likely exhaust energy reserves before an animal can reach the coast, whereas swimming at less than 5–7 cm s − 1 is inefficient because of the overhead of nonswimming, inactive metabolism. Even at the model‐predicted optimal swimming speed near 8 cm s − 1 , pueruli are likely at the limit of their endurance upon completion of migration. Reduced energy reserves at the outset due to prior poor feeding, or delays encountered en route due to unfavorable currents, could lead to exceeding the stored reserves of the pueruli, and death. Potentially, relatively small shifts in coastal ocean climate conditions could generate marked changes in recruitment to important spiny lobster fisheries.