‘Drivin' with your eyes closed’: Results from an international, blinded simulation experiment to evaluate spatial stock assessments

Spatial models enable understanding potential redistribution of marine resources associated with ecosystem drivers and climate change. Stock assessment platforms can incorporate spatial processes, but have not been widely implemented or simulation tested. To address this research gap, an international simulation experiment was organized. The study design was blinded to replicate uncertainty similar to a real-world stock assessment process, and a data-conditioned, high-resolution operating model (OM) was used to emulate the spatial dynamics and data for Indian Ocean yellowfin tuna (Thunnus albacares). Six analyst groups developed both single-region and spatial stock assessment models using an assessment platform of their choice, and then applied each model to the simulated data. Results indicated that across all spatial structures and platforms, assessments were able to adequately recreate the population trends from the OM. Additionally, spatial models were able to estimate regional population trends that generally reflected the true dynamics from the OM, particularly for the regions with higher biomass and fishing pressure. However, a consistent population biomass scaling pattern emerged, where spatial models estimated higher population scale than single-region models within a given assessment platform. Balancing parsimony and complexity trade-offs were difficult, but adequate complexity in spatial parametrizations (e.g., allowing time- and age-variation in movement and appropriate tag mixing periods) was critical to model performance. We recommend expanded use of high-resolution OMs and blinded studies, given their ability to portray realistic performance of assessment models. Moreover, increased support for international simulation experiments is warranted to facilitate dissemination of methodology across organizations.Peer reviewe

Impaired reproduction in three-spined sticklebacks exposed to ethinyl estradiol as juveniles

To investigate the population-level effects of exposure to environmental endocrine disrupters, a mesocosm-scale study was carried out in which the reproductive performance of groups of free-spawning three-spined sticklebacks, Gasterosteus aculeatus, exposed as juveniles to a model estrogen, was assessed. Juvenile sticklebacks were exposed to ethinyl estradiol (EE2) at measured concentrations of (mean ± SEM) 1.75 ± 0.37 ng L–1 and 27.7 ± 1.08 ng L–1 for 4 wk posthatch and then reared thereafter in pristine lake water until they reached adulthood. Exposure to the higher EE2 concentration resulted in the occurrence of ovotestis among males, whereas no gonadal abnormalities were evident among males exposed to the lower concentration of EE2. In addition, when spawning was allowed in the mesocosm environment, fewer nests were built per male, and fewer eggs were deposited per nest, in the group exposed to 27.7 ng L–1. Males from this group also exhibited a less intense nuptial coloration than control males. In the group exposed to 1.75 ng L–1 EE2 posthatch, significantly fewer nests were built than in the control group. These results demonstrate that the timing of exposure to estrogenic contaminants, in developmental terms, is critically important. Short-term exposure to estrogens as juveniles can clearly influence reproductive performance as adults, despite all growth and development subsequent to the exposure period taking place in an estrogen-free environment. In addition, these results suggest that reproductive dysfunction can occur even in fish with no gross abnormalities in gonadal structure. This suggests that the absence of gonadal intersex is not a reliable indicator of the reproductive potential, or estrogen-exposure history, of fish populations or the only important factor involved in compromising the reproduction of estrogen-exposed fish

Data for "Variation in Upper Plate Crustal and Lithospheric Mantle Structure in the Greater and Lesser Antilles from Ambient Noise Tomography"

This is the phase velocity information and the shear wave model for the g-cubed paper: &quot;Variation in Upper Plate Crustal and Lithospheric Mantle Structure in the Greater and Lesser Antilles from Ambient Noise Tomography&quot;</span