Offshore wind - diadromous fish: review - January 2024

Glossary

acoustic telemetry: a telemetry method that uses a sound signal for tracking animals

active swimming: a fish that is actively swimming and not simply drifting passively with the current

anadromous: fish that spawn in freshwater and then migrate to salt water

Carlin tag: a non-telemetry method to mark fish; a plastic tag is sutured to the dorsal musculature

catadromous: fish that spawn in salt water and then migrate to freshwater

coastal: near shore, other than within clearly defined estuaries.

data storage tag: telemetry method that records data such as location and environmental variables

diadromous: fish that migrate between freshwater and salt water

epipelagic: the uppermost zone of ocean water column

Fraunhofer distance: wavelength of a radio wave, which provides the limit between the near and far field

fullness index: index used to calculate feeding intensity; F = 10000 x stomach content mass/total body mass

Fulton’s K index: condition factor of a fish calculated using the length and weight (K = weight / length³)

glass eels: eel post-larval stage after completion of leptocephalus and until full pigmentation

glochidia: larval stage of freshwater pearl mussel

Innovation and Targeted Oil & Gas (INTOG) leasing areas: cover small scale innovation projects (<100MW) and offshore wind farms that target electrification of oil and gas installations

iteroparous: reproductive strategy where an individual spawns in multiple cycles during its lifetime

kelt: adult salmonid that has spawned and is migrating back to the sea

leptocephalus: larval stage of eel

maiden returning adult: an adult salmonid that is returning from its marine migration for the first time

multiple spawner: a fish that has spawned at least once previously

nacelle: a part of a wind turbine that contains the gearbox, shafts, generator and brake

near-shore: the area of the sea in the vicinity of the coastline, including estuaries

partial migration: phenomenon where a portion of the population migrates while the rest stay resident

particle motion: in relation to sound; transmission of oscillatory motion between neighbouring particles

passive movements: a fish that is passively moving with water currents and is not actively swimming

Petersen disc: a non-telemetry method to mark fish; consists of two plastic discs attached to a fish with a pin or wire (usually on gill cover or back muscle)

post-smolt: salmonid smolt (migratory juvenile) that has entered the marine environment

potadromous: a fish that migrates within freshwater only (i.e. along a river gradient or between rivers and lakes for example)

precocious parr: salmonid (usually male) that sexually matures in freshwater at small size and age; may subsequently migrate to sea.

satellite telemetry: telemetry method; a data logger or archival tag which transmits collected data (e.g. GPS location) through the satellite system

sea trout: the marine migratory (anadromous) form of brown trout

semelparous: reproductive strategy where an individual spawns only once during its lifetime

shadow flicker: the flickering effect caused when rotating wind turbine blades periodically cast shadows to the ground or water below

Shannon-Weiner Index: also called Shannon-Weiner Species Diversity Index; used to measure the diversity of species in a community

smolt: a juvenile salmonid that is undertaking its first seaward migration; between parr and post-smolt stages

sound pressure: local pressure deviation from the ambient atmospheric pressure, caused by a sound wave (SI unit pascal, Pa)

straying: phenomenon where a returning adult salmonid enters a different river than its natal river; cf. effective straying rate which is the proportion of fish that actually spawn and successfully contribute to the next generation in a non-natal river

succession: the process by which the mix of species and habitat in an area, changes over time