Future ocean temperature impacting the survival prospects of post-larval spiny lobsters.

Spiny lobster post-larvae undertake an extensive migration from the open ocean to the coast, during which time their swimming is fueled solely by energy reserves accumulated through their preceding larval phase. We assessed the influence of future ocean temperatures on the swimming behavior and energy use of migrating post-larvae of Sagmariasus verreauxi, by experimentally swimming post-larvae for up to 6 days at three temperatures and measuring the lipid and protein used, and observing their time spent actively swimming. Increasing the temperature from 17 °C to 23 °C doubled the energy utilized by post-larvae while swimming, while also reducing the time they spent swimming by three times. Therefore, increasing ocean temperatures appear to greatly affect the energetic cost and efficiency of shoreward migration of post-larvae in this lobster species, with the potential to markedly impact post-larval recruitment into coastal populations under future scenarios of ocean warming.

Correction: Mesoscale circulation determines broad spatio-temporal settlement patterns of lobster.

[This corrects the article DOI: 10.1371/journal.pone.0211722.].

Mesoscale circulation determines broad spatio-temporal settlement patterns of lobster.

The influence of physical oceanographic processes on the dispersal of larvae is critical for understanding the ecology of species and for anticipating settlement into fisheries to aid long-term sustainable harvest. This study examines the mechanisms by which ocean currents shape larval dispersal and supply to the continental shelf-break, and the extent to which circulation determines settlement patterns using Sagmariasus verreauxi (Eastern Rock Lobster, ERL) as a model species. Despite the large range of factors that can impact larval dispersal, we show that within a Western Boundary Current system, mesoscale circulation explains broad spatio-temporal patterns of observed settlement including inter-annual and decadal variability along 500 km of coastline. To discern links between ocean circulation and settlement, we correlate a unique 21- year dataset of observed lobster settlement (i.e., early juvenile & pueruli abundance), with simulated larval settlement. Simulations use outputs of an eddy-resolving, data-assimilated, hydrodynamic model, incorporating ERL spawning strategy and larval duration. The latitude where the East Australian Current (EAC) deflects east and separates from the continent determines the limit between regions of low and high ERL settlement. We found that years with a persistent EAC flow have low settlement while years when mesoscale eddies prevail have high settlement; in fact, mesoscale eddies facilitate the transport of larvae to the continental shelf-break from offshore. Proxies for settlement based on circulation features observed with satellites could therefore be useful in predicting broadscale patterns of settlement orders of magnitudes to guide harvest limits.

Stroke patterns and regulation of swim speed and energy cost in free-ranging Brünnich's guillemots.

Loggers were attached to free-ranging Brünnich's guillemots Uria lomvia during dives, to measure swim speeds, body angles, stroke rates, stroke and glide durations, and acceleration patterns within strokes, and the data were used to model the mechanical costs of propelling the body fuselage (head and trunk excluding wings). During vertical dives to 102-135 m, guillemots regulated their speed during descent and much of ascent to about 1.6+/-0.2 m s(-1). Stroke rate declined very gradually with depth, with little or no gliding between strokes. Entire strokes from 2 m to 20 m depth had similar forward thrust on upstroke vs downstroke, whereas at deeper depths and during horizontal swimming there was much greater thrust on the downstroke. Despite this distinct transition, these differences had small effect (<6%) on our estimates of mechanical cost to propel the body fuselage, which did not include drag of the wings. Work stroke(-1) was quite high as speed increased dramatically in the first 5 m of descent against high buoyancy. Thereafter, speed and associated drag increased gradually as buoyancy slowly declined, so that mechanical work stroke(-1) during the rest of descent stayed relatively constant. Similar work stroke(-1) was maintained during non-pursuit swimming at the bottom, and during powered ascent to the depth of neutral buoyancy (about 71 m). Even with adjustments in respiratory air volume of +/-60%, modeled work against buoyancy was important mainly in the top 15 m of descent, after which almost all work was against drag. Drag was in fact underestimated, as our values did not include enhancement of drag by altered flow around active swimmers. With increasing buoyancy during ascent above 71 m, stroke rate, glide periods, stroke acceleration patterns, body angle and work stroke(-1) were far more variable than during descent; however, mean speed remained fairly constant until buoyancy increased rapidly near the surface. For dives to depths >20 m, drag is by far the main component of mechanical work for these diving birds, and speed may be regulated to keep work against drag within a relatively narrow range.