Almost the entire coastline of Anglesey was designated as an Area of Outstanding Natural Beauty (AONB) in 1966 to protect the aesthetic appeal and variety of the island's coastal landscape and habitats from inappropriate development. The AONB is about 221 km2 and it is the largest AONB in Wales, covering one third of the island.

Surveys
2.1 Survey catchments

Ten catchments were selected working in a clockwise direction around the coast, from the Afon Braint in the southwest to the Afon Lleiniog in the southeast.

The selection of the individual survey streams was based on a variety of factors as outlined below:

1. 1)  The selected catchments give a broad geographical coverage of the Island, capturing the diverse landscape and some of the major urban areas.

2. 2)  The rather limited existing information (primarily NRW WFD) is largely focused on these larger catchments and this becomes important in providing base data when trying to demonstrate any improvements arising from future work.

3. 3)  These rivers exhibit some of the highest discharge rates on the Island and as a result, negative impacts from pollutants, have a significant impact on coastal bathing water quality. Given the economic value of tourism on Anglesey any water quality improvements on these rivers would help to sustain this valuable resource.

4. 4)  Being the larger waterbodies on the Island, there was an opportunity to investigate the possibility of developing marketable brown trout fishing that would benefit the local economy.

   2.2 Walkover Survey Methodology

   The survey data was captured as annotations on a 1:10000 scale map and associated photographs.

   A photograph was taken of each source/issue and comments recorded as appropriate, for example providing information on the land use on the relevant bank(s) and possible habitat restoration options. Photographs were also taken at intervals along the survey length to capture the typical habitat at that point.

   Invasive weeds such as Himalayan Balsam and Japanese Knotweed reduce biodiversity, increase bank erosion and restrict access to the watercourse. The presence of these species was recorded wherever possible and notes were taken indicating the extent or density at a given point.

   The identification of obstructions to fish migration is a fundamental element of any catchment fisheries study and opening up the watercourse is often the first action in a management plan and often the most cost effective.

   To supplement the physical site data recorded for each obstruction an objective assessment of the impact on migration was made, placing each barrier into one or more of three main categories.
   All fish migration barriers, including road-crossings, can be placed into three broad categories as outlined below: temporal, partial, and total.

Temporal Barriers

At temporal barriers, the obstruction may block upstream migration of adult fish at certain flows (normally low), allowing them to eventually negotiate the barrier as flows change. The delay imposed by such an obstruction can limit the distance adult fish migrate upstream before spawning. This may result in underutilisation of upstream habitat and superimposition of redds in lower stream reaches. Even if the barrier is eventually negotiated by adult fish, excess energy is expended and may result in their death prior to spawning or reductions in viability of eggs and offspring.

Migrating adults and juveniles concentrated below temporal obstructions are vulnerable to predation by a variety of avian and mammalian species, and to poaching by humans. In addition, this reduction in available stream habitat creates competition for space and food among adult and juvenile salmonids and other aquatic species, year- round.

Partial Barriers

Partial barriers are often crossings that prevent upstream juvenile passage but allow adult passage over some or all flows. Although not well understood, awareness has developed among the fisheries community regarding the importance of upstream movement within the life history of juvenile and resident fish.

Juvenile Atlantic salmon spend up to four years in freshwater (typically two or three years) prior to subsequent downstream migration.
During this period, they will often migrate up smaller streams to find more suitable habitat and better food sources

Total Barriers

The definition of a total barrier is to confirm that there is no upstream movement of aquatic fauna through the barrier. This is often difficult to assess as some barriers that have been ranked as temporal or partial merely achieve this ranking due to the occurrence of very occasional flood events that may permit the passage of some species and life-stages of fish in a very short time frame.

This does not however take into consideration the cumulative action of a number of barriers on the same system that effectively cause a total block to migration.

2.3 Volunteer training

A total of thirteen local volunteers were trained in the recording methods outlined above. An initial workshop on the 23rd April 2017 at the Cefni reservoir fishermen’s hut gave a theoretical explanation of the survey methods and the background and rational for the project. This was followed on the 28th May with a practical session in the field and numerous small group or one to one demonstrations as the project progressed.

Additional meetings were held with interested landowners, angling associations, North Wales Wildlife Trust, Dŵr Cymru and NRW in efforts to link with current works and to develop possible future partnerships.

2.4 Limitations of the assessment

A walkover river survey is, by its very nature, a snapshot in time, capturing data over a matter of a few days at a specific point in the season. Waterways are incredibly dynamic systems, changing their physical structure over time and can alter significantly after spate events.
On Anglesey, the seasonal variation in vegetation cover is particularly pronounced and it is often nigh on impossible to navigate a lowland waterway in the summer months due to the dense riparian growth. As a result, many surveys had to take place later in the year as the cover died back.

Flow variation is particularly important when trying to assess potential barriers to fish migration and ideally, a structure should be visited under a range of conditions to evaluate it thoroughly. Pollution events are also more likely to occur when levels are high and the drainage network is flowing swiftly. These conditions are unfortunately also the ones that are most likely to wash away any evidence of such an event and it is a case of being in the right place at the right time to capture the data.

3 Catchment Summaries

3.1 Introduction

Over the course of the ten catchment surveys a vast amount of data was collected by volunteers and project staff, including annotated maps, notes and hundreds of photographs. The main rivers have all been surveyed along with sections of major tributaries but the process is an ongoing one with volunteers still keen to survey smaller waterbodies that they have a personal interest in. As has been previously mentioned, other areas need to be evaluated at different times of year or a range of flow levels to better understand their impacts.

The following catchment summaries are intended to give a broad overview of each surveyed waterbody, giving an indication of its physical characteristics and the main factors impacting the overall habitat quality.
The catchments are described working upstream from the estuary to a point in the headwaters where the river becomes too small to be of value to both migratory and resident salmonid populations.

You can download the full report for each ten areas here.