Abstract
Vineyard Wind 1 LLC (Vineyard Wind), in collaboration with the University of Massachusetts Dartmouth’s School for Marine Science and Technology (SMAST), has developed a monitoring plan to assess the potential environmental impact of the proposed offshore renewable energy development on marine fish and invertebrate communities in Lease Area OCS-A 0501 (the “VW1 Study Area). One component of the monitoring plan is a demersal trawl survey. The trawl survey is modeled after the Northeast Area Monitoring and Assessment Program (NEAMAP), a regional survey used to assess nearshore fish communities. The data collected from this survey is intended to provide baseline information on species abundance, distribution, population structure, and community composition to be used in a future impact analysis. Pre-construction monitoring started in 2019. The data provided in this report is the third and final year of pre-construction monitoring, which included three seasonal surveys. Similar fisheries studies are being conducted within Lease Area OCS-A 0534 (the “534 Study Area”) and within Lease Area OCS-A 0522 (the “522 Study Area”); these studies are reported separately.
Three seasonal trawl surveys were conducted using a commercial fishing vessel in the fall of 2021, winter of 2022, and summer of 2022. Twenty tows were conducted each season in the VW1 Study Area. An additional 20 tows were collected in a neighboring region, which served as a control (Control Area). Tow locations were randomly selected using a spatially balanced sampling design. A standardized bottom trawl with a 1” knotless liner was towed behind the vessel for 20 minutes at 3 knots. Acoustic sensors were used to ensure the net’s performance by monitoring the trawl geometry. The catch was sorted by species. Aggregated weights, as well as individual fish lengths and weights, were collected.
A total of 120 tows were completed throughout the year split equally between the VW1 Study Area and the Control Area, and among the three seasons. In general, the data were similar to that observed during the previous survey years. The catch data obtained shows a dynamic area with a diversity of marine species. A total of 40 species were collected; however, the majority of the catch was comprised of a small subset of the observed species. The five most abundant species (butterfish, scup, little skate, Atlantic herring, and spiny dogfish) accounted for 87% of the catch weight in the Control Area and 81% of the catch weight in the VW1 Study Area. Interannual changes in abundance varied amongst species. All species caught displayed seasonal variations in distribution and abundance. The data indicated a unique assemblage of species and abundance in each season. Species composition during the fall and winter surveys showed strong similarity to that observed in the same surveys in 2019/2020 and 2020/2021. The summer survey exhibited variationsin the community composition compared to the same seasons in 2019 and 2020. The changes in species composition may be linked to changing seasonal water temperatures. Bottom water temperature has remained relatively consistent across the fall and winter surveys between survey years. Conversely, bottom water temperature during the summer surveys has varied annually. In 2020, the summer bottom water temperature was 5⁰C warmer than in the 2019 survey. The species assemblage during 2020 shifted toward heattolerant species (i.e., scup, butterfish, summer flounder) while species that prefer cooler water (i.e., silver hake, winter skate) appeared to move to deeper water. Summer bottom water temperature in 2022 was intermediate to the two previous surveys (2019 & 2020). No differences in species assemblages were observed between the VW1 Study Area and Control Area.
An updated power analysis was conducted using data aggregated from three survey years. The results indicate that the current bottom trawl survey effort would provide reasonable “power” to detect small to medium scales of change in abundance for the most common species if changes in abundance do occur. Additional data only caused small changes to the Coefficients of Variation (CVs) for most species. Common species (i.e., species frequently observed regardless of abundance), including little skate and Atlantic longfin squid, exhibited low variability resulting in the projected ability to detect a 25% change in abundance or greater. Most commercial species, including summer flounder, black sea bass, and silver hake, exhibited modest variability. The current sampling effort should be able to detect 30 – 40% changes in abundance.