The biology of the American horseshoe crab, Limulus polyphemus, is well documented-including its dietary habits, particularly the ability to crush shell with gnathobasic walking appendages-but virtually nothing is known about the feeding biomechanics of this iconic arthropod. Limulus polyphemus is also considered the archetypal functional analogue of various extinct groups with serial gnathobasic appendages, including eurypterids, trilobites and other early arthropods, especially Sidneyia inexpectans from the mid-Cambrian (508 Myr) Burgess Shale of Canada. Exceptionally preserved specimens of S. inexpectans show evidence suggestive of durophagous (shell-crushing) tendencies-including thick gnathobasic spine cuticle and shelly gut contents-but the masticatory capabilities of this fossil species have yet to be compared with modern durophagous arthropods. Here, we use advanced computational techniques, specifically a unique application of 3D finite-element analysis (FEA), to model the feeding mechanics of L. polyphemus and S. inexpectans: the first such analyses of a modern horseshoe crab and a fossil arthropod. Results show that mechanical performance of the feeding appendages in both arthropods is remarkably similar, suggesting that S. inexpectans had similar shell-crushing capabilities to L. polyphemus. This biomechanical solution to processing shelly food therefore has a history extending over 500 Myr, arising soon after the first shell-bearing animals. Arrival of durophagous predators during the early phase of animal evolution undoubtedly fuelled the Cambrian 'arms race' that involved a rapid increase in diversity, disparity and abundance of biomineralized prey species.

Casitas are artificial shelters used by fishers to aggregate Caribbean spiny lobsters (Panulirus argus) for ease of capture. However, casitas may function as an ecological trap for juvenile lobsters if they are attracted to casitas and their growth or mortality is poorer compared with natural shelters. We hypothesized that juvenile lobsters may be at particular risk if attracted to casitas because they are less able than larger individuals to defend themselves, and do not forage far from shelter. We compared the nutritional condition, relative mortality, and activity of lobsters of various sizes in casitas and natural shelters in adult and juvenile lobster-dominated habitats in the Florida Keys (United States). We found that the ecological effects of casitas are complex and location-dependent. Lobsters collected from casitas and natural shelters did not differ in nutritional condition. However, juvenile lobsters in casitas experienced higher rates of mortality than did individuals in natural shelters; the mortality of large lobsters did not differ between casitas and natural shelters. Thus, casitas only function as ecological traps when deployed in nursery habitats where juvenile lobsters are lured by conspecifics to casitas where their risk of predation is higher. These results highlight the importance of accounting for animal size and location-dependent effects when considering the consequences of habitat modification for fisheries enhancement.

Accelerometers are useful devices for monitoring the activity of a variety of lobster species, both in the laboratory and the field. While the method has proven beneficial for determining when animals are active, it is more difficult to determine the actual distance animals travel or the intensity of their movements based on accelerometry. To achieve this goal, we monitored American lobsters, Homarus americanus H. Milne-Edwards, 1837, fitted with HOBO accelerometer dataloggers and Vemco V13AP accelerometer transmitters in the laboratory and simultaneously obtained time-lapse digital videos of their behavior. We used these data to convert accelerometer outputs to distances moved per unit time. The outputs of both types of accelerometers were well correlated with distance traveled. We then used this information to analyze data obtained in a previous study, using the same HOBO accelerometers. This made it possible to calculate to what extent activity and the distance traveled per hour changed on a seasonal basis over a year. This analysis also revealed that lobster activity in the field was significantly greater than activity in the lab at the same time of year, within similar enclosures. Overall, these results demonstrate that accelerometry is a suitable and accurate method for monitoring the relative activity of lobsters over long periods in the laboratory and field and the results compare favorably with other published studies of lobster movements. Lobster activity has been measured in multiple ways in the laboratory, including using shuttle boxes (Zeitlin-Hale and Sastry 1978, Reynolds and Casterlin 1979), infrared light and reed-switch gates (Jury et al. 2005), running wheels and treadmills (O'Grady et al. 2001, Jury et al. 2005), video systems (Lawton 1987, Cooke et al. 2004), and strain gauges (Koike et al. 1997). In the field, acoustic or electromagnetic tracking, telemetered tilt switches, and scuba observations have also been used to estimate the daily activity and movements of lobsters (

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Marine reserves are essential spatial conservation tools that have been shown to work alongside fishery management strategies to provide benefits to ecosystems and communities. Reserves often incentivize local tourism, which can provide the impetus for reserve creation but may have negative impacts on the ecosystem. The COVID‐19 pandemic paused global travel and provided an unprecedented opportunity to compare short‐term changes in exploited populations, during the reprieve from visitation provided by this ‘anthropause’, with the results of long‐term conservation management. Repeated surveys of Caribbean spiny lobster and Nassau grouper were conducted at popular dive and snorkel locations within a Bahamian no‐take reserve and surrounding areas during peak visitation prior to travel restrictions and immediately after restrictions were lifted. Repeated survey results were referenced against surveys over a broader area, including another Bahamian Bank, to examine the consistency of effects and how the ease of access for fishers impacted abundance. In the reserve, lobsters were encountered in significantly greater abundances, and significantly greater sizes of both lobster and grouper were observed in repeated surveys. Significantly more grouper were encountered during the repeated survey within the reserve after travel restrictions, but lobster abundances did not change significantly. Over a broader scale, lobster abundance was significantly greater further from population centres. Observed lobster abundance was affected by habitat and inferred fishing pressure, whereas observed grouper abundance was affected by survey depth, effort, and habitat. Marine reserves had clear benefits for both species and likely facilitated an increase in grouper abundance during the anthropause. Lobsters are a sustainably managed stock in The Bahamas, whereas grouper are a threatened species that appear to have benefited from an unplanned fishery restriction. Well‐managed marine reserves enhance populations long term and can have additive effects with fisheries management over short timescales.