DOI: 10.5061/dryad.b5mkkwhm3
title: Data from: Removing plastic benefits marine ecosystems: Evidence from four decades of endangered seal entanglement

description: Abandoned, lost, or otherwise discarded fishing gear (ALDFG) causes
 tremendous harm to marine species and ecosystems. To mitigate the
 destruction wrought by these ocean plastics, various cleanup programs have
 been established, though benefits of such efforts to marine species and
 ecosystems have not been demonstrated. We examined over 40 years of
 Hawaiian monk seal marine debris entanglement records before and after
 large-scale marine debris removal efforts were initiated in the
 Northwestern Hawaiian Islands, demonstrating a significant reduction in
 entanglement rate where debris removal effort was most concentrated.
 Large-scale and sustained removal of ALDFG meaningfully benefits marine
 ecosystems and has the potential to be transformational in restoration
 efforts.
description: These data are based on tagging and visual monitoring of weaned
 Hawaiian monk seal pups in the Northwestern Hawaiian Islands, including
 observed incidents of entanglement in marine debris. The data were
 processed to calculate a robust rate of entanglement for comparison among
 populations and years. Poisson regression analyses were then used to
 determine factors, including the effect of large-scale marine debris
 removal, on the entanglement rate. Information on the timing, location,
 and amount of marine debris removed from islands and marine habitats were
 also summarized.
description: # Removing plastic benefits marine ecosystems: evidence from four decades
 of endangered seal entanglement
 [https://doi.org/10.5061/dryad.b5mkkwhm3](https://doi.org/10.5061/dryad.b5mkkwhm3) The file *weaned pup entanglement rates.csv* contains calculated rates of weaned Hawaiian monk seal entanglement, which were based on visual monitoring if tagged pups at six subpopulation in the Northwestern Hawaiian Islands. The file contains the following columns: row# = row index  year = year subpop = specified monk seal subpopulation, coded as follows: ffs = French Frigate Shoals, lay = Laysan Island, lis = Lisianski Island, phr = Pearl and Hermes Reef, mdy = Midway Atoll, kur = Kure Atoll. expdays = number of observed weaned pup exposure days summed over all pups at a given subpopulation in a given year. This is the total number of days that pups were exposed to entanglement risk as weaned pups when standardized observation effort was also being conducted. effdays = number of days during which observers were present at subpopulation each year (for reference, not used in analysis), obsent = number of qualifying weaned pup entanglements observed. Qualifying entanglements were those detected during an interval of standardized observation effort. rate = the weaned pup entanglement rate calculated as 1000 x obsent/expdays. removal = an indicator variable where 0 indicates a year prior to marine debris removal efforts and 1 indicates a year after marine debris removal efforts. Missing data code: NA The file *debris removal mass.csv* contains information on the amount of marine debris removed from six monk seal subpopulation sites in the Northwestern Hawaiian Islands. The file contains the following column: row# = row index year = year subpop = specified monk seal subpopulation, coded as follows: ffs = French Frigate Shoals, lay = Laysan Island, lis = Lisianski Island, phr = Pearl and Hermes Reef, mdy = Midway Atoll, kur = Kure Atoll. kg = kilograms of marine debris removed tally = indicates whether the mass value is annual or cumulative (up to and including the referenced year) mt = metric tons of marine debris removed. ## Description of the data and file structure *weaned pup entanglement rates.csv* is a comma separated value (.csv) file containing quantitative data on the rate at which weaned Hawaiian monk seal pups were entangled in marine debris at 6 subpopulations over many years. Each row contains the relevant year and subpopulation, and the factors used to calculate the rate, along with the calculated rate. A 0 or 1 in the final column indicates whether the year was before or after large-scale marine debris removal efforts in the Northwestern Hawaiian Islands had begun. *debris removal mass.csv* is a comma separated value (.csv) file containing quantitative data on the mass of marine debris removed from six sites where six Hawaiian monk seal subpopulations occur. Each row contains the amount removed for a given year and subpopulation. There are two rows for each year and subpopulation. One provides the amount removed that year and the other provides the cumulative removal up to and including that year. ## Code/Software The file *Entanglement rate analysis code.R* is an R script that reads in provided data and conducts Poisson regression analysis of weaned Hawaiian monk seal entanglement rates in relation to a number of variables. Model selection information is also derived. RStudio Version 2023.06.2+561 (2023.06.2+561) was used to run this code. The package reshape2 was used.