Gully monitoring review : 2021

A review of baseline data and trends for the Gully Marine Protected Area (MPA) monitoring indicators was conducted, as well as discussion of advances in understanding of the ecosystems in the Gully and linkages to the broader Scotian Shelf - Bay of Fundy bioregion. There was general agreement that the wide array of data being gathered, through a range of research and monitoring activities in and around the Gully, has increased understanding of its ecosystems and potential human impacts. Though this information provides a broad context to describe the ecosystem, more work is required to fully implement a standardized, long-term monitoring program, to help ensure that monitoring efforts continue to advance our understanding and reporting on the status of conservation priorities, and to detail how human activities influence conservation priorities so that mitigation options can continue to be developed as needed. The development of most monitoring indicators is still at an early stage. It is important that as data are collected and monitoring programs implemented, periodic assessments of effectiveness (i.e., the ability to detect change) are undertaken to guide improvements in the program’s ability to detect and characterize change. Available data give some indication of the success of the Gully in meeting its conservation objectives, but it is not yet possible to say whether it has fully achieved all objectives. Data were collected for most indicators though time-series analysis was only available for some, in particular those focusing on cetaceans and oceanography. While most indicators revealed little or no detectable change over various timescales, some notable trends were detected and are reported below. Trends reported here are considered to be meaningful (statistically significant) for the Gully, but they may not be reflective of broader regional trends (i.e., may not be reflective of the conservation status of a regional population). For example: Abundance of the Scotian Shelf population of Northern Bottlenose Whales (NBW; Hyperoodon ampullatus) has been increasing since 2010, following a period of decline before 2004. Sightings of calves have increased since 1998. Overall male and mature male NBW are more marked (scarred) than females and juveniles. Some mark types (notches, back indents) have increased over the period 1988–2019, which could in part be related to the age of identified individuals. The prevalence of anthropogenic injuries appears stable to increasing over this time period, at an annual rate of 1.7 individuals gaining entanglement or propeller scars per year. Within the Gully, number of sightings of other cetacean species have shown varied trends, since 1988: Sowerby’s Beaked Whale (Mesoplodon bidens) and Pilot Whales (Globicephala melas) sightings have increased, sightings of Humpback Whale (Megaptera novaeangliae), Fin Whale (Balaenoptera physalus), and some dolphin species have decreased, and sightings of Blue Whales (Balaenoptera musculus) increased in the mid-2000s but have since declined. Oceanographic properties in the Gully fluctuate considerably from year to year due to natural variability. Over the last two decades, when systematic monitoring has taken place, the only significant trend observed has been an increase in mid-depth (100–400 m) temperature due to the growing influence of warm slope water in the offshore region. Based on the joint DFO-Industry longline survey, Atlantic Halibut (Hippoglossus hippoglossus) biomass appears to be increasing in the Gully at a rate of about 5% per year, consistent with a population-wide trend. Observed densities of floating debris in the MPA declined between 1990 and 2019. Ocean ambient noise levels in the Gully were examined based on an analysis of Passive Acoustic Monitoring (PAM) datasets obtained from one deep-water site in the Gully between 2012 and 2019. No strong trend in low frequency long-term (6-yr) deep ocean ambient noise levels was observed over this period, though the 100 Hz to 500 Hz frequency band showed a slight increasing rate of approximately 0.30 dB per year. In situ baseline surveys using underwater imagery for benthic species and habitats have been undertaken throughout the Gully MPA, although no sites have been revisited to assess trends in indicators for coral abundance, diversity, and health. Gaps in spatiotemporal coverage for at-sea seabird surveys persist within the Gully and adjacent areas. Three key ecological attributes with associated indicators were identified for seabirds as a conservation priority: areal density, relative use of Gully habitat, and biodiversity. However, potential trends in these indicators have not been fully explored. Offshore petroleum drilling activity around the MPA has ceased; the Deep Panuke and Sable Offshore Energy projects were decommissioned at the end of 2020. Potential impacts of climate change on the Gully include rising ocean temperatures, ocean acidification, reduced dissolved oxygen availability, and novel combinations of environmental variables, which could lead to physiological responses, reduced growth and survival rates, and potential range shifts in species including NBW. Climate indices (initial focus on temperature, pH, and dissolved oxygen) and biological indicators predicted to respond to climate change should be monitored over the long-term. Long-term monitoring programs within the MPA provide an invaluable empirical basis on which to evaluate performance, efficacy, and change over time. Science programs can also make cost-effective contributions through short-term, targeted baseline and characterization work, including process-oriented studies to discover critical pathways that offer potential for more efficient monitoring in the future.

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