Many natural objects exhibit radial or axial symmetry in a single plane. However, a universal tool for simulating and fitting the shapes of such objects is lacking. Herein, we present an R package called ‘biogeom’ that simulates and fits many shapes found in nature. The package incorporates novel universal parametric equations that generate the profiles of bird eggs, flowers, linear and lanceolate leaves, seeds, starfish, and tree‐rings, and three growth‐rate equations that generate the profiles of ovate leaves and the ontogenetic growth curves of animals and plants. ‘biogeom’ includes several empirical datasets comprising the boundary coordinates of bird eggs, fruits, lanceolate and ovate leaves, tree rings, seeds, and sea stars. The package can also be applied to other kinds of natural shapes similar to those in the datasets. In addition, the package includes sigmoid curves derived from the three growth‐rate equations, which can be used to model animal and plant growth trajectories and predict the times associated with maximum growth rate. ‘biogeom’ can quantify the intra‐ or interspecific similarity of natural outlines, and it provides quantitative information of shape and ontogenetic modification of shape with important ecological and evolutionary implications for the growth and form of the living world.

Studies typically assess the effects of temperature on development time, larval drift, and fisheries recruitment in American lobster at a range of constant temperatures. However, in nature, lobster larvae are exposed to varying temperatures, which might result in different development times than would be predicted from mean temperatures alone. To investigate this hypothesis, we conducted a modelling exercise in which we simulated larval development from hatch through stages I–IV under different combinations of mean and variance in temperature. Two thermal scenarios were modelled, the first based on estimated (i.e. interpolated by a model from empirical data) recent historical mean and variability of sea surface temperatures (SSTs) experienced by developing larvae in specific parts of the species' range, and the second based on a broad range of simulated combinations of mean and variability in temperature, including conditions that may be experienced by larvae in the future. The model calculated development times using daily SSTs and temperature-dependent development equations from previous studies of warm- and cold-water origin larvae. For warm-origin larvae, higher variability in temperature resulted in shorter development times at very cold and very warm mean temperatures, and longer development at intermediate mean temperatures, than lower (or no) variability. For cold-origin larvae, the effect of variable temperature was overall much smaller, and opposite to that for warm-origin larvae at very cold and very warm mean temperatures. These results show that lobster larvae experience meaningful variability of water temperature in nature, and that this variability can markedly impact larval development. Thermal variability therefore should be considered when estimating development and drift of lobster larvae, including under scenarios of climate change.

We used a biophysical model to estimate for the first time the effect of larval drift on potential connectivity among American lobster (Homarus americanus) fisheries management areas over the geographic range of the species. The model predicted drift of larvae over distances of 50–805 km (mean = 129 km), which connected many management areas and caused marked spatial heterogeneity in retention and self-seeding versus export and import of larvae by different fisheries areas. Including mortality functions in the model resulted in less drift and settlement and had complex effects on the amount, but not the incidence, of potential connectivity among fisheries. The model’s predictions received support from comparison of predicted settlement to landings 6 or 7 years later in some, but not all, parts of the model domain. Although improvements are still needed to capture larval behaviours and spatial variability in larval release and mortality across the species’ range, this information is important to lobster fisheries management because the amount and direction of connectivity among fisheries can inform cooperative management strategies to sustain interconnected fisheries.

This paper reports the results of a ten-year monitoring program of an Atlantic Canadian population of green crabs,Carcinus maenas, in the Minas Basin of the Bay of Fundy. Intertidal densities, sex and reproductive ratios, juvenile recruitment, subtidal catch-per-unit-effort (CPUE), and sizes of crabs in this population were recorded from 2008 to 2017. In 2013 intertidal densities, mean crab sizes, subtidal CPUE, and proportions of crabs mature and reproducing all dramatically decreased to all-time lows, and large crabs virtually disappeared from the population. From 2014 to 2017 the population partially recovered but remained in an altered state. Potential causes of interannual changes to this population were investigated by correlating intertidal densities to 257 monthly environmental variables and performing stepwise multiple regression analyses. Crab densities in a given year were best explained by potential settlement during the summer and the maximum sea-surface temperature during March of the same year. However, potential roles of other factors (e.g., autumn winds, summer temperatures, North Atlantic Oscillation index) could not be ruled out. Changes in abundances of other species in the area, particularly predators and prey of green crabs, have also been observed and present possible alternative causative agents that should be investigated. Populations of other marine species in the Gulf of Maine-Bay of Fundy region within which the Minas Basin is situated have also been reported to have undergone dramatic changes in and after 2013, suggesting the occurrence of some oceanographic event or regime shift in the region. Declines to the monitored crab population in this study may have resulted from this same 2013 event. These observations have implications for recruitment to marine populations in this region.