Availability of bait supplies

Availability of bait supplies

Despite falling numbers of sea anglers, and evidence for a reduction in the numbers of bait collectors active in some regions during the past decade, wild bait supplies are reported by bait diggers to be increasingly scarce in some regions. The retail trade also reports that existing sources of bait from commercial bait collectors and farmed sources are completely inadequate to meet demand, both in the UK and overseas. Bait diggers consulted identify several factors thought to be responsible:

loss of bait beds through pollution, land claim or coastal works changing current and sediment regimes;

closure of bait beds as a result of increased restrictions by landowners and managers (e.g. in nature reserves, ports and harbours, and on recreational beaches); and

over-exploitation of bait stocks, causing populations to dwindle in heavily exploited areas.

Thus, despite a reduction in the numbers of sea anglers, overall demand by sea anglers for wild-caught bait is high. It may even continue to rise unless bait farming significantly increases supply to domestic markets. Apart from bait digging by anglers for their personal use, future demand may be met by increased commercial bait digging or increased production from bait farms in the UK, Netherlands and Ireland, or, potentially most worryingly, imports of non-native bait species from the USA or East Asia.

Concerns raised by species collection and opportunities for mitigation.

Issue	Reasons for concern	Potential for mitigation
Impacts on bird populations	Disturbance while feeding/roosting (particularly of wintering or migrant birds) caused by presence of collectors on the shore is well documented. Scale varies: species have different tolerances to disturbance and radii of exclusion around bait diggers. Prey species depletion, as a result of collection of target species, destruction of non-target species, or habitat and prey community change. Not as well documented.	Difficult – bait collectors and feeding birds favour the same habitats. No entry to areas used by feeding &/or roosting birds will be most effective. The minimum size of the exclusion zone will be dependent on the tolerance to disturbance and vulnerability of the species involved and the size and structure of the site. Need not be a permanent exclusion area.
Impacts on intertidal habitats	Damage/change as a result of species collection is well documented for many habitats. Sediment habitat damage from bait digging is most significant in sheltered habitats (estuaries and inlets), where holes can persist for weeks or months. Recovery is rapid in high-energy environments. Mixed sediments are seriously affected, with fine sediments lost and stones uncovered, and very slow recovery. Overturning rocks and stones while searching for intertidal species damages this habitat. The habitat impacts of installation of crab shelters have not been studied. They provide hard substrata in sediment areas, increasing biodiversity, but will likely alter water exchange through tidal flow and wave action, particularly after overgrowth by algae, potentially changing the nature of the habitat (research is required into their effects).	Most effective mitigation measure is back-filling of holes and trenches left after baitdigging and levelling of any remaining spoil mounds. Recovery will still be slow in low energy environments, where exclusion zones may be necessary to retain undisturbed habitats. Replacement of boulders turned while searching for crab is essential. Both of the above measures are recommended in all codes of conduct but relatively rarely observed. Difficult to promote without personnel on site. Bait collectors may be best able to promote their own codes in an area. Effects of crab shelters on habitats and potential for mitigation are unstudied. There are likely to be optimum densities of shelter placement for maximum yields and minimum habitat alteration.
Stocks of target species	Target species are depleted by over-collection and/or through habitat damage/change that affects recovery rates. Common, fecund, short-lived species recover quickly (blowlug Arenicola marina, winkles Littorina littorea, and most populations of king ragworm Nereis virens). Shore crab (Carcinus maenus) are likely to fall in this category, but harvesting effects are not studied. No information is available for black lug Arenicola defodiens recovery rates. Less common, slow-reproducing species are of greater concern (long-lived bivalves, white rag or catworms Nephtys species, and some king ragworm N. virens populations). Few studies of recovery of these species have been undertaken.	Undisturbed upper shore nursery grounds, subtidal stocks or intertidal refuges are essential to maintain stock recruitment. Backfilling will restore dug areas more quickly. Rotational use of blowlug A. marina beds will maximise yields, but complex to administer and may conflict with other user group interests. Insufficient information available to recommend similar mitigation measures for blacklug A. defodiens, shore crab C. maenus and white rag or catworms Nephtys species. Artificial restocking from local brood stock reared in bait farms may be possible for many species. Full protection is advisable for part of very long-lived, potentially slow recruiting species’ populations (e.g. razor shells Ensis spp.).
Stocks of non-target infauna	Non-target species are lost or depleted through physical damage or habitat change as a result of collection. Sedentary, long-lived, slow-reproducing species will be most seriously affected. Few studies have been undertaken of recovery of such species after disturbance, but this process will be lengthy for species living for over ten years and recruiting infrequently. Common, short-lived species recruit and recover quickly (>12 months).	Backfilling and restoration of habitat will reduce incidental mortality. Full protection advisable for beds of very long-lived, slow recruiting bivalves and fragile burrowing echinoderms. They will not survive intensive collection or disturbance, and may take a decade or more to recover original population structure, even if local sources of recruitment remain intact in refuges nearby.
Water quality/ pollution	Digging sheltered sediment releases fine materials into suspension and frees heavy metals and contaminants if anoxic sediments are disturbed. Environmental effects of increased turbidity and heavy metal pollution are well documented. Water quality/ pollution may alter target species availability and affect the health of collectors.	Minimal potential for mitigation, other than exclusion of baitdigging from most heavily polluted sites.

The information presented in the above table is summarised from the following pages, which describe in more detail the scientific evidence for the above impacts of bait collection and cite references to source literature. The Appendix summarises the literature reviewed.

The table below falls outside the main scope of this review (which is concerned with the effects of species collection on the natural intertidal environment), but is included in order to present the other impacts or conflicts that may arise between bait collectors and other shoreline uses.

Potential sources of impact or conflict between intertidal species collection and other shoreline uses, and opportunities for mitigation.

Shoreline use	Potential source of conflict with bait collection	Potential for mitigation of effects
Recreation	Intensive bait collection on sandy beaches is unsightly. The mounds and soft pits produced by bait digging cause potential inconvenience or even danger to bathers, walkers, and riders. Crab shelters on soft sandy beaches may provide unexpected obstructions and cause injury.	Infilling holes and levelling spoil mounds will resolve visual problems, but sediment may remain soft and treacherous in dug areas for several tidal cycles. Crab shelters laid flat on sediment are less dangerous than those embedded at an angle. Zonation of digging or crab collecting and other beach activities is an important option for mitigation. Some local authorities use byelaws to control bait collection on recreational beaches.
Landscape	The visual appearance of excavated holes and spoil heaps from bait digging, or numerous peeler crab shelters in muddy estuaries is often of concern to visitors and local residents.	Infilling holes and levelling spoil mounds will improve appearance of bait beds. Crab tiles laid flat on sediment are less visually obtrusive than when driven in at an angle.
Heritage/ archaeology	Collection (digging/stone turning) is known to cause damage to intertidal archaeological sites, such as fish traps, wrecks, or field walls and other drowned structures.	Mitigation of damage caused by digging large holes or overturning stones in archaeological sites unlikely to be possible. Exclusion will be necessary.
Launching, mooring and navigation	Digging may undermine slipways and moorings, causing problems (even danger) when vessels launched across the shore. Crab aggregation devices (tiles, pipes and tyres) protruding from soft sediment may potentially cause damage to beached or moored vessels, inconvenience or injury to individuals wading to boats, and obstruct navigation channels or anchorages.	Incompatibility of these activities indicates that zonation could be appropriate to separate bait digging and/or the installation of crab shelters from coastal structures, moorings, anchorages and navigational channels. Zonation may be undertaken by voluntary agreement or byelaw. Harbour Authorities are increasingly concerned by these activities, and many now control them under byelaw.
Coastal structures	Bait digging may undermine or cause damage to coastal or flood defences, jetties and other structures.	As above. Byelaws are already in use in many areas to control bait digging near coastal structures.
Commercial fisheries	The impact of intertidal collection on commercial species, whether removal of undersized individuals or loss of prey populations, is not well studied or understood. Habitat effects, which could affect areas or species covered by Several Order, are described above.	Effects not well understood, but likely to be minor in comparison with the direct effects of commercial fisheries on stocks under consideration. Mitigation measures will depend on species involved.

Potential for interaction between shoreline species collection and other users

Coastal features or user groups potentially affected by shoreline species collection

Type of species collection or associated activity

Birds

Habitats

Target stocks

Non-target spp.

Pollution

Recreation

Landscape

Archaeology

Launching

Moorings

Coastal or flood defence

Navigation

Fisheries

Worm pumping at LWST on exposed sandy beaches

Worm digging, sheltered to moderate exposed shores

Worm digging on very sheltered mixed sediments

Worm digging – Nephtys spp., mod. Exposed shores

Bivalve digging

Winkle collection from rocky shores

Stone turning

Installation and use of peeler crab shelters (tiles etc.)

Bait dragging on mud flats, from boats at high tide

Introduction of non-native bait species imported/farmed

Shading indicates the potential likelihood of a negative interaction taking place between shoreline species collection and nature conservation features or other users. Any effects of bait collection may vary greatly between sites.

None or unlikely

Possible

Probable

The above table provides a matrix illustrating the potential severity of the impact or conflict that may arise as a result of intertidal species collection. It is a rough indication of effect only, and the conflicts, if any, which may be experienced at any one site as a result of the activities listed, will vary greatly from site to site. A blank version of such a matrix may be a useful approach for management committees when considering the range of activities underway within their local site, and the likely impact of these on other uses. The matrix may be shaded according to the extent of the activity at their site, and would be expected to demonstrate a lesser overall effect than indicated above.

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