DOI: 10.5061/dryad.hdr7sqvkb
title: Biofouling data from underwater surveys of commercial ships in Canada

description: Ship biofouling is a major vector for the introduction and spread of
 harmful marine species globally. Comprehensive underwater sampling and
 video recording of ship hulls was conducted to assess biofouling extent
 (percent cover, total abundance and species richness) on a subset of ships
 arriving to Canadian waters. The dataset includes
 underwater biofouling assessments from 53 commercial ships
 arriving at Halifax, Nova Scotia (20 international
 ships), Vancouver, British Columbia (20 international ships)
 during 2007–2009, and Churchill, Manitoba (11 international and
 2 domestic ships) in 2010–2011. Potential explanatory variables
 in the dataset include ship size, typical sailing speed, port residence
 time, age of antifouling coating system and travel history (number of
 biogeographic realms visisted, and average, minimum and maximum
 port latititude).
description: Underwater surveys were conducted by professional divers while
 ships were stationary in port. Divers surveyed both sides of the hull of
 each ship from bow to stern and bottom to waterline, although access to
 the mid-ship section was normally limited by the size of the gap between
 the hull and the berth bed and wall. The rudder sides, bottom, leading and
 trailing edges, propeller nose and blades, rope guard, stern tube,
 sea-chests, bow-thruster tunnel and grating, bulbous bow, stem and main
 hull were inspected for every ship. Physical samples were collected at
 each location where growth was observed, whereas a value of zero organisms
 was recorded in locations where no growth was found. Physical sampling was
 not random, but aimed to include the highest possible number of organisms
 and species. Average abundances m^2 and for the whole ship were estimated
 using percent cover information from random video-transects of the entire
 hull. Sampling was conducted at each location with 1–3 replicate 20 · 20
 cm magnetic quadrats attached to the hull of each vessel, or equivalent
 surface area at uneven locations where the use of the quadrat was not
 practical. Barnacle samples were scraped into re-sealable plastic bags and
 a suction device mounted on a scraping blade was used to collect soft
 growth. Two-L water samples were also collected from the dock at mid-hull
 depth as controls. The water volume of each hull fouling sample was
 measured at the dock using a graduated cylinder, and organisms in the
 equivalent volume of control water sample were subtracted from abundance
 counts (see below). Species present in control water samples were
 subtracted from species richness estimations. For a subset of ships, hull
 samples were examined by eye at the dock, prior to fixation, to determine
 if organisms were dead or alive when collected. However, this analysis was
 limited to barnacles, amphipods, chironomids, mites, large bivalves and
 gastropods as remaining groups were not large enough to be checked
 reliably. Specimens that appeared alive (e.g. movement, valve/plate
 closure) were preserved separately. All samples were sieved through a 40
 um mesh and preserved in 95% ethanol at the dock. Information including
 the list of ports-of-call since last dry-dock or 1 year previous to
 sampling, antifouling protection and the sheet of particulars were
 collected from the crews of each vessel. All samples were processed in the
 lab to estimate abundances and conduct taxonomic identifications.
 Macroalgae were not present in samples. Instead, algal cover was
 restricted to relatively thin films lacking reproductive structures, thus
 only organisms from selected samples were identified at a coarse taxonomic
 level. For this reason, efforts were focused on invertebrate
 animals.
description: The in-water sampling design did not allow divers to open and
 sample inside sea-chests and other protected locations, although sampling
 was conducted from the grating covering the sea-chests. Therefore, hull
 fouling was probably underestimated in such locations.