4.8. Shellfish

  1. Shellfish is a colloquial and fisheries term that generally refers to exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms but also includes cephalopods. Note that species such as horse mussel Modiolus modiolus and ocean quahog Arctica islandica, along with other non-commercial species of shellfish and habitats created by shellfish species (such as mussel beds) are considered benthic species and are characterised within volume 3, appendix 8.1. Shellfish communities contribute to the biodiversity of the benthic ecosystem and are an important link in the food chain, both as predators and prey. The population structure of shellfish stocks around the UK is not fully understood, with assessments largely based on previous fishing and landings data and sometimes surveys (e.g. Nephrops) (Mesquita et al., 2016). Only a limited number of species have a stock assessment undertaken regularly (i.e. edible crab, velvet swimming crab, European lobster, Nephrops and scallops) (Marine Scotland, 2013), therefore, commercial landings data in the area provides an overview of species likely to be present.
  2. As described previously, there are a number of commercially important shellfish species within the fish and shellfish ecology study area. Commercial landing data can be used as a proxy for identifying species present in the fish and shellfish ecology study area and in the vicinity of the site boundary, which include Nephrops, edible crab, European lobster, velvet swimming crab, king scallop, whelks and squid, as described in volume 3, appendix 12.1. There are consistently high landings of Nephrops, and medium to low landings of European lobster, edible crab, velvet swimming crab, king scallop, whelks, razor clam Solenidae spp., squid, and octopuses (between 2009 and 2015: Mesquita et al., 2016, 2017, and 2020 to 2021: Marine Scotland, 2021; 2022c). Occasionally caught species include green crab, northern stone crab Lithodes maja, spiny lobster Palinurus elephas, common prawn Palaemon serratus and queen scallop (Marine Scotland, 2021).
  3. Site-specific DDV and epibenthic beam trawl surveys for Berwick Bank Offshore Wind Farm recorded Nephrops, edible crab and king scallop, albeit in low abundances (SSER, 2022). Shellfish found in high abundances in epibenthic trawls included brown shrimp and other shrimp species (Pandalidae spp.), however, these are not a key target of commercial fisheries within the area.
  4. Site-specific surveys for Seagreen Alpha and Seagreen Bravo (now referred to as Seagreen 1 and 1A) (Seagreen Wind Energy Ltd., 2012) also reported edible crab, velvet swimming crab and king scallop in epibenthic beam trawls.

4.8.1. King and Queen Scallop

  1. Scallops show a preference for areas of clean firm sand, fine or sandy gravel and may occasionally be found on muddy sand. Distribution of these species is invariably patchy (Carter, 2009; Marshal and Wilson, 2009) but the areas with greatest abundance tend to be areas of little mud and with good current strength.
  2. King scallop achieve reproductive maturity between three to five years, live upwards of 15 years and are evidenced to be most abundant in depths of 20 m to 70 m (Howarth and Stewart, 2014; Salomonsen et al., 2015; Cappell et al., 2018). Queen scallop are usually found on sand or gravel to depths up to 100 m but also occur amongst horse mussel beds (MarLIN, 2023).
  3. Key physical differences between king and queen scallop are illustrated as queen scallop possessing two distinctive curved shells, while the king scallop’s upper shell is predominantly flat and are typically larger overall. Queen scallop stocks are known to be more highly mobile than king scallops, especially within the summer months when queen scallops are more actively swimming.
  4. In Scottish waters, scallops spawn for the first time in the autumn of their second year, and subsequently spawn each year in the spring or autumn. After settlement, scallops grow until their first winter, during which growth usually ceases. Thereafter, growth resumes each spring and ceases each winter, causing a distinct ring to be formed on the external surface of the shell (Scottish Government, 2012).
  5. King scallop are targeted commercially through dredge fisheries in the fish and shellfish ecology study area, although not within the site boundary. Within the fish and shellfish ecology study area, the majority of the activity, albeit moderate, is concentrated within ICES rectangles outside of the site boundary (refer to volume 3, appendix 12.1). Queen scallop were recorded during the site-specific benthic surveys across the site boundary (refer to volume 3, appendix 8.1, annex A).

4.8.2. European Lobster

  1. European lobster can be found from Scandinavia to north Africa and throughout the British coasts on rocky substrata, down to depths of 60 m. After moulting in summer, European lobster mate and larvae will remain planktonic for up to four weeks before settling onto the seabed in solitary shelters (Cefas, 2020a). They are usually relatively sedentary with some inshore to offshore migration recorded in some locations (Cefas, 2020a). European lobster are actively fished, mostly in inshore waters, with low landings recorded for the ICES rectangles that overlap with the site boundary (41E9, 42E9, 42F0) (refer to volume 3, appendix 12.1).

4.8.3. Edible Crab

  1. Edible crab are a relatively long-lived species that is found on all coasts around Britain from the intertidal zone down to depths of 100 m. They live on rocky, gravelly substrate within which they bury into. Following spawning there is a larval dispersal phase of around 30 to 50 days. Stock boundaries are not well defined and edible crabs move over large areas. Females have been found to travel long distances from spawning areas (Cefas, 2020b). For females carrying eggs, there is an inactive brooding period in winter. The eggs hatch in spring and summer and larvae remain in the plankton for about five weeks. Edible crab mating activity peaks in summer and spawning follows later in autumn or during winter (Cefas, 2020b). Like European lobster, there are low landings of edible crab within the ICES rectangles that overlap with the site boundary (41E9, 42E9, 42F0) (refer to volume 3, appendix 12.1).

4.8.4. Velvet Swimming Crab

  1. Velvet swimming crab can be found around the coast of Britain and are found on stony/rocky substrate intertidally and down to depths of 100 m (Howson and Picton, 1997). Velvet swimming crab are targeted by commercial fisheries with higher commercial values available in continental Europe and they are often caught alongside European lobster and edible crab (refer to volume 3, appendix 12.1).
  2. Velvet swimming crab were also recorded within the Berwick Bank Offshore Wind Farm (SSER, 2022) and therefore can be assumed to be present in the vicinity of the site boundary.

4.8.5. Squid

  1. Loliginid squid species are reported to be found over sand and muddy bottoms (Wilson, 2006) and are mostly demersal in nature, therefore are often captured as bycatch in demersal fisheries (Bellido et al., 2001). Ommastrephid squid species however are pelagic and are therefore often under-represented in trawl survey data and fisheries statistics. Research on squid indicates that they are probably batch spawners, however, this can vary depending on species, with some species utilising hard substrate for spawning purposes (Guerra and Rocha, 1994). Squid are typically short-lived species, with some loliginids recorded to live between 12 and 16 months (Guerra and Rocha, 1994). Many squids are semelparous, meaning that they will only spawn once and die shortly after (Hendrickson and Hart, 2006). In Scottish waters, squid exhibit a distinct seasonal migration pattern, travelling up to 500 km from the west coast of Scotland to the east coast in the winter months (Hastie et al., 2009). Squid are targeted by commercial fisheries, although main areas of fishing activity are within coastal waters and do not directly overlap the site boundary (refer to volume 3, appendix 12.1).

4.8.6. Nephrops

                        Desktop study

  1. Nephrops, known variously as the Norway lobster, Dublin Bay prawn, langoustine or scampi, are slim, orange pink lobsters which grows up to 25 cm long, and are considered to be the most commercially important crustacean in Europe (Bell et al., 2006). Nephrops are exploited throughout their geographic range, from Icelandic waters to the Mediterranean Sea and the Moroccan coast.
  2. Nephrops are opportunistic predators, primarily feeding on crustaceans, molluscs and polychaete worms. They inhabit muddy seabed sediments and show a strong preference for sediments with more than 40% silt and clay (Bell et al., 2006). They build and spend significant amounts of time in semi-permanent burrows which vary in structure and size but typically range from 20 cm to 30 cm in depth (Dybern and Hoisaeter, 1965). Due to strong habitat preferences, distribution patterns of Nephrops are determined by the presence of suitable habitats, with higher abundances found on more favourable substrates.
  3. Female Nephrops usually mature at three years of age and reproduce each year thereafter. After mating in early summer, Nephrops spawn in September and carry eggs under their tails (described as being 'berried') until they hatch in April or May. The larvae develop in the plankton before settling to the seabed six to eight weeks later (Coull et al., 1998). Within the fish and shellfish ecology study area, unspecified intensity nursery and spawning grounds for Nephrops are present within the south-west (56.57 km from the site boundary) and northern sections (45.94 km from the site boundary) but neither grounds coincide with the site boundary itself ( Figure 4.6   Open ▸ ).

                        Site-specific surveys

  1. As discussed in paragraph 159, Nephrops display a strong preference for muddy sediments (silt and clay), therefore with the majority of the site boundary characterised as sandy substrata, this area is considered unsuitable for Nephrops. No observations were made of Nephrops during the site-specific epibenthic trawl survey or combined grab and DDV sampling conducted within the site boundary. The biotope that Nephrops are typically associated with (sea pen and burrowing megafauna communities) (JNCC, 2021e) was not found to be present across the site boundary. As such, the site boundary is unlikely to be an important area for Nephrops.

4.8.7. Whelk

  1. Common whelk are an opportunistic carnivorous species, distributed throughout the north Atlantic Ocean. This species will typically inhabit subtidal areas, although they have been recorded on all types of seabed substratum including gravel, sand, mud and rock (Haig et al., 2015).
  2. They are commercially exploited in UK waters, with much of the catch exported to East Asia (Eastern Inshore Fisheries and Conservation Authority (IFCA), 2020). They are vulnerable to exploitation as they are slow-growing and slow to reach sexual maturity (Eastern IFCA, 2020). Furthermore, recent studies have demonstrated that whelk show local differences in growth rates, suggesting that they are caught and landed before reaching sexual maturity in some areas (Haig et al., 2015; McIntyre et al., 2015).

4.9. Designated Sites

  1. With the exception of sea trout, European eel and sparling, all the migratory fish discussed in section 4.7 are listed as Annex II qualifying features under the Habitats Directive (Council Directive 92/43/EEC) which provides them with protection and ensures their populations and habitats are maintained or restored through the designation of a SAC. Only Atlantic salmon and both lamprey species are qualifying features of SACs within the regional fish and shellfish ecology study area ( Table 4.7   Open ▸ ). Other non-migratory fish and shellfish species that are qualifying features of designated sites have been considered for the fish and shellfish assessment where applicable to this topic ( Table 4.7   Open ▸ , Figure 4.19   Open ▸ ). Further details on the assessments against the conversation objectives of each European site (i.e. SAC) and each qualifying feature is presented in the Report to Inform the Appropriate Assessment (RIAA).

 

Table 4.7:
Designated Sites with Fish and Shellfish Qualifying Features within the Fish and Shellfish Ecology Study Area

Table 4.7: Designated Sites with Fish and Shellfish Qualifying Features within the Fish and Shellfish Ecology Study Area

Figure 4.19:
Designated Sites with Fish as Qualifying Features

Figure 4.19: Designated Sites with Fish as Qualifying Features