Fish

Introduction

Marine fish can be categorised into:

• Bony fish, which have an internal calcium skeleton (such as herring and plaice).
• Cartilaginous fish, whose skeleton is primarily made of cartlidge and represent the oldest surviving jawed vertebrates. The sharks, skates and rays fall into this category and are collectively known as elasmobranchs.
• Jawless fish (lampreys and hagfish). These distinctive, elongated fish do not have jaws, fins or stomachs and have a distinctive elongated shape and feed by suction with a round muscular mouth and rows of teeth.

The number of fish in Wales is difficult to estimate accurately – up to 500 species have been recorded from the UK and Ireland, with at least 250 found off the Welsh coasts. The majority of these are bony fish, with approximately 25 species of cartilaginous fish (skates, rays, sharks) and 3 jawless fish (lampreys and hagfish).

Marine fish occupy a wide variety of niches in Wales. Many inhabit nearshore areas and are familiar to us as inhabitants of rockpools, like the blennies, gobies and shannies. These contrast with species such as bluefin tuna Thunnus thynnus, which can grow to over 400 kg and are found seasonally off the south west coast of Wales. The 10m basking shark is a species which also undergo large migrations and are occasionally seen off the west coasts of Wales feeding on plankton between May and September.

Marine fish exhibit a huge variety of body diversity, from slender elongated pipe fish and eels to the distinctive flattened shape of the bony flatfish (e.g. plaice) and skates / rays. There is an equally vast array of life history behaviours and reproduction strategies within marine fish. Benthic fish, found on the seabed, can be relatively sedentary; the cling fish has a modified sucker allowing it to stick to the underside of rocks, the male will stay under a rock to guard their eggs. This contrasts with pelagic species such as herring and sandeel, which shoal in large numbers and spawn over huge areas of the seabed. Skates and rays are famously known for producing intricate ‘mermaids’ purses’, these are tough egg cases attached to the seabed where the embryos of the young develop. The empty cases can often be found washed up on beaches. The iconic long snouted seahorse Hippocampus guttulatus is rare in Wales. Males famously brood the eggs in their ventral pouch, and they have the ability to rapidly transform colour patterns to blend with their immediate surroundings.

Some fish species are migrants to Welsh waters, seen especially in south and West Wales, these include iconic species such as the Ocean Sunfish Mola mola, the heaviest bony fish in the world. They are usually encountered whilst drifting on the surface, with their dorsal fin visible flopping side to side.

Some Welsh fish are diadromous, spending part of their life cycle in freshwater environment and part in the marine environment. Fish that are hatched in freshwater, live most of their life in the marine environment and then migrate back to freshwater to spawn are known as anadromous. These include Atlantic salmon Salmo salar, river and sea lampreys Lampetra fluviatilis and Petromyzon marinus and allis and twaite shads (Alosa alosa and Alosa fallax). The European eel Anguilla Anguilla has a similar but reversed pattern, it hatches in the sea, and travels to rivers where it spends most of its adult life stages before it returns to the sea to breed. These diadromous species face threats to their movement up and downstream and a number of initiatives are ongoing to remove barriers and make passage easier. Both Atlantic salmon and European eel are under particular threat in Wales and have experienced huge declines in the last 30 years.

Action for marine fish in Wales

Sharks, Skates and Rays (elasmobranchs)

Relatively little is known about sharks, skates and rays as a group, however, they have a significant cultural and conservation importance in Wales. Project SIARC (Sharks Inspiring Action and Research with Communities) is specifically delivering a fisher-integrated research programme to gather data on elasmobranchs and their associated habitats in two Special Areas of Conservation in Wales. Project SIARC is a multidisciplinary project, focussing on elasmobranchs of conservation importance, including the Critically Endangered (IUCN red list) Angelshark Squatina squatina. Combining both social and biological sciences the project aims to address critical data gaps in the ecology of elasmobranchs, diversify opportunities for marine conservation, generate a greater appreciation for the underwater environment and inspire the next generation. The project is led by the Zoological Society of London (ZSL) and Natural Resources Wales (NRW) and is being completed in partnership with six delivery partners and 13 collaborative partners.

Migratory fish

A number of projects in Wales are the focus of removing barriers to fish migration, allowing easier passage from marine environments into the upper reaches of Welsh rivers for spawning. The LIFE Dee River project is a £6.8m project focussed on the Dee in east Wales, which is focussed heavily on improving the numbers of salmon and lamprey, which includes removing constraints to fish migration and installing fish passage solutions.

Another LIFE project called ‘Four Rivers for LIFE’ is underway on four rivers designated as Special Areas of Conservation in south Wales (Teifi, Cleddau, Tywi and Usk) which likewise aims to restore protected diadromous fish species throughout their riverine habitat.

Afonydd Cymru also have projects ongoing to remove barriers to migration, especially for salmon.

Resources

SIARC | Sharks Inspiring Action and Research with Communities

Wales Angelshark Action Plan

The Shark Trust

Shark Trust Great Eggcase Hunt

Natural Resources Wales / NRW launches £6.8 million LIFE Dee River project

Natural Resources Wales / Four Rivers for LIFE