Monk Seal Ecosystem Model Data: A Comparison of Ecosystem Structure and Energy Flows of Monk Seal Populations from Laysan Island and French Frigate Shoals in the Northwestern Hawaiian Islands

To understand various ecosystem dynamics that could explain observed changes and differences in monk seal biomass at French Frigate Shoals (FFS) and Laysan (LAY), Ecopath with Ecosim (EwE) version 6.4.4 modeling software was used to conduct two types of simulations, sensitivity (to understand the system) and hindcast (to evaluate drivers of monk seal population dynamics). EwE models for LAY and FFS were developed and model output was compared between the 2 models. The model output data included in the data sets represent the most important conclusions as reported in the publication from this study. These are (1) the mean of the last 5 years of each perturbation for sensitivity assessment; and (2) hindcast simulations. The first data set was used to understand the main drivers of the trophic structure and energy flow in the ecosystems. Four perturbation scenarios were simulated for a time span of 40 years (2010 through 2049): (a) baseline (compare static structural ecosystem composition between FFS and LAY), (b) altered predator abundance (30% decrease in biomass of main predators in the ecosystem), (c) altered monk seal prey abundance (30% decrease in biomass of main monk seal prey groups, with and without bottomfish to test how much bottomfish accounts for changes, and (d) altered primary productivity (change productivity annually by 10% for both phytoplankton and benthic algae through an annual forcing factor of 0.9 and 1.1 on both groups). The hindcast simulations were performed to evaluate the importance of historical stressors to monk seal population dynamics by selecting the best-fit model for the monk seal biomass time series (1998-2015). Stressors included were (a) fishing with time series based on commercial fishery data, (b) environment with time series of the monthly PDO index as a multiplier for primary productivity, (c) additional mortality simulated with a constant removal of monk seals of varied intensities, and (4) combinations of these 3 stressors (2a and 2c being the most important with regard to the observed trend in monk seal population). Time series observation data of monk seal biomass and benthic bottomfish biomass, as well as catch time series of bank sharks (only for FFS), benthic and demersal bottomfish, bank jacks, and macroheterotrophs (lobsters) were loaded into Ecosim for model fitting. Refer to Weijerman et al (2017) for complete details.

Tags: biology, biomass, biosphere, bottomfish fishery, central pacific ocean, country/territory, doc/noaa/nmfs/pifsc, earth science, ecological dynamics, ecological modeling, ecopath with ecosim, ecosystem modeling, ecosystem sciences division, ewe, french frigate shoals, french frigate shoals (24n166w0001), hawaii, hawaiian monk seal, honolulu, laysan, laysan island (25n171w0001), marine biology, marine mammals, model output, monk seal, national marine fisheries service, nmfs, noaa, north pacific ocean, northwestern hawaiian islands, northwestern hawaiian islands (28n178w0000), numeric data sets, nwhi, ocean basin, oceans, pacific islands fisheries science center, pacific ocean, papahanaumokuakea marine national monument, pifsc, pinnipeds, pmnm, protected species division, psd, recovery, u.s. department of commerce, united states of america, us doc, vertebrates, zoology
Organization: National Oceanic and Atmospheric Administration, Department of Commerce