Abstract
This post-construction monitoring report has been prepared for Moray Offshore Windfarm (East) Limited (Moray East) as part of the Project Environmental Monitoring Programme (PEMP) required as part of their Section 36 Consents. This report describes the post-construction element of Condition 26 of the PEMP in relation to cod spawning and satisfies Condition 11 (Piling Strategy (PS)), Condition 34 (Telford & Stevenson), and Condition 33 (MacColl) of Moray East Section 36 consent conditions. Whilst the North Sea cod (Gadus morhua) stock is assessed as a single unit, there is evidence of sub-stock structuring (Fox et al., 2008 and ICES, 2007). Cod spawning grounds have been defined in the Moray East site (i.e. Coull et al., 1998 and Ellis et al., 2010); however, the degree of spawning activity currently taking place in this area is largely unknown. The objective of this survey was to collect data to characterise the spatial and temporal distribution of spawning cod activity in and around the Moray East site. The survey methodology was designed in consultation with Marine Scotland Science (MSS) and Marine Directorate Licensing and Operations Team (MD-LOT). The survey was conducted in two trips (Trip A and Trip B) between 12th March 2024 and 29th March 2024 coinciding with the peak cod spawning season. Eight stations were sampled during each trip. In line with the 2019 pre-construction cod survey, sampling was undertaken using a commercial rock-hopper otter trawl with a 120 mm mesh cod-end, fitted with a 40 mm blinder. The catch from each otter trawl was emptied into the hopper, sorted into baskets by species and photographed. The length, sex and spawning condition of each cod was identified, recorded and their gonads photographed. Over the course of the two survey trips (Trip A and Trip B), cod were caught at five of the eight stations sampled, with a maximum of three cod caught at a single station (OT35, Trip A). Of the 10 cod caught in total, nine stage III (“spawning”) cod were caught (OT36, OT39, OT38, OT27, and OT35 Trip A; OT39, Trip B), with one juvenile recorded (OT08, Trip A). Only one cod was caught during Trip B (25th March – 29th March 2024).,which was of maturity stage “spawning (cessation)”.
Cod catch rates were calculated using the net sensor data outputs (swept area per tow). MSS guidance (derived from Wright et al., 2006) definition of spawning areas based on Catch Per Unit Effort (CPUE) was used to determine whether significant cod spawning occurred at any of the stations surveyed. Three categories were assigned based on the values provided by MDS:
- ‘Not important’ for spawning cod (≤15 spawning cod/km2 );
- ‘May be important’ for spawning cod (>15 to ≤ 75 spawning cod/km2 ); and
- ‘Spawning area’ (>75 spawning cod/km2 ).
The analysis of CPUE of spawning cod found no locations fell within the threshold of a cod “spawning area”. Four locations fell within the threshold of “may be important” to spawning cod in Trip A, and one in Trip B; however, it should be noted that this is based on one individual of cod of spawning status caught at three of the stations during Trip A, and one station during Trip B. All other stations fell within the “not important” for spawning cod threshold.
The results of the surveys suggest that cod spawning occurred in the survey area pre-construction and that this continues to be the case post-construction. Both surveys found cod in relatively low numbers and no sampling stations were identified as “spawning areas” based on analysis of spawning cod CPUE between the pre- and post-construction.