Habitat damage

Impacts on bait species

Impacts on non target species

Impacts on other shore users

Other impacts

Mitigation

In many cases shoreline species collection activity is not thought to be incompatible with nature conservation objectives in marine sites. Some scientific and site management case studies, however, demonstrate that habitat damage and alteration, damage to non-target species, and bird disturbance and prey depletion may arise from this activity, particularly if carried out on a large scale. These are summarised below. In such situations, shoreline species collection (whether for bait or for food) may require mitigating action if intertidal nature conservation objectives are not to be compromised.

Literature review indicates that habitat damage on sediment shores is likely to be most serious in low energy environments, where sediments are poorly sorted (mixtures of stones and mud), often polluted, and recovery rates from bait digging can be very slow. Such sites are frequently located in estuarine areas and other inlets, close to centres of population, exposed to heavy use by collectors, and also subject to many other development pressures.

More wave exposed, sandy shores are not as significantly affected by bait digging, and the use of bait pumps in these locations appears to cause negligible damage. Very large-scale use by mechanical bait dredgers has the potential to cause significant damage even in these situations.

Some studies of boulder turning for peeler crabs have demonstrated that serious habitat damage, particularly on sheltered, stable boulder shores, can occur when boulders are not replaced. The effects of wide-scale introduction of crab shelters in estuaries on habitats and species have not been studied, but are considered likely to be significant in some areas. Investigations are required of the impacts of introduction of crab shelters into inlets on the sediment habitats occupied by large numbers of shelters, bird populations, and crab populations. In particular, the optimum density of crab shelters, both for minimising habitat effects and maximising yields should be determined as a matter of urgency. Shelter density is probably unnecessarily high in some areas. The effect of the orientation of shelters (flat versus driven at an angle into the sediment) should also be examined. Much of this work might be undertaken, at least initially, through undergraduate projects.

Most populations of bait species are not threatened by collection, even locally. Many of the animals used by anglers are common and widely distributed, with their life cycles and ecology enabling a quick recovery from low population levels. Exceptions to this rule are the catworms Nephtys species and unusual long-lived king ragworm Nereis virens populations like that studied in the Menai Strait. Heavy bait digging pressures may seriously affect the survival of local populations of these groups.

In the case of the Menai king ragworm, a single unique population could be endangered without the controls on this activity planned within the proposed Marine Nature Reserve. Studies of other reported populations of unusually large king rag worms Nereis virens (e.g. in Milford Haven) are needed to determine whether these also have the characteristics of those in the Menai Strait, and whether management of these stocks are necessary. This could be a useful undergraduate project, modelled on those carried out in the Menai Strait.

There is very little information available on the impacts of collection of large numbers of peeler and softshell crab Carcinus maenus, and potential means of mitigating these. Undergraduate projects could compare population structure in exploited and unexploited areas and estuaries.

More information is required on the biology, ecology, and exploitation of the valuable bait species, the black lugworm Arenicola defodiens, including survival after tail loss and eversion of internal organs. Would closure of beds during breeding periods result in increased levels of recruitment, and in which habitats do the larvae live? This information would help to determine the impacts of bait collection on this species (presently considered to be relatively small) and establish appropriate bait collection management regimes, if necessary. Some life cycle information is apparently already known, but commercially confidential and unpublished. Field studies might be undertaken as undergraduate projects, and more detailed research as a postgraduate study.

Not much is known about the biology of white ragworms Nephtys species and potential for mitigation of the impacts of collection of this genus. Research into captive populations might provide some useful information (some is likely already known, albeit unpublished and in confidence), as well as determining the potential scope for restocking depleted bait beds of this and other species by breeding local brood stock in bait farms.

The non-target invertebrates most affected by bait collection are large, long-lived, slow-growing infaunal species that may be fragile, easily damaged by bait diggers and slow to recolonise areas. Under-boulder fauna, which are dependent upon a stable and very specialised habitat, are also severely affected by boulder-turning by collectors in search of peeler crab. Diverse communities characteristic of some poorly-sorted sheltered sediments may also be damaged by bait collection or the introduction of crab shelters. Mechanical bait dredging causes a high loss of biomass in areas dredged.

Disturbance of feeding shore birds caused by the presence of bait collectors on the shore at low water in some sensitive areas is a very serious problem. The removal of invertebrate biomass (bird food) is also potentially significant, particularly if mechanical dredging takes place. Most methods of bait collection (probably excluding bait pumping) may cause significant habitat and non-target species damage, and all may restrict the areas of shore available to feeding birds.

Bait collection activity can incompatible with certain fisheries - mainly through damage to intertidal cockle and mussel beds, or increased access difficulties to shellfish beds.

Habitat damage and alteration may also be incompatible with some recreational uses, harbour operations and archaeological heritage. Problems caused include deterioration in the aesthetic appearance of dug shores and crab shelters, human safety, and physical damage to vessels and structures.

Competition between different groups of bait collectors (anglers vs. commercial collectors, ‘professional’ vs. ‘unemployed’ commercial collectors, and/or locals vs. visiting collectors) has sometimes been reported when over-exploitation of bait stocks takes place. It can be extremely difficult to resolve such competition through voluntary agreement or self-regulation where visitors are involved, and because of the difficulty of proving a distinction between commercial and non-commercial activity. Many bait collectors are in favour of a system for licensing bait diggers (requiring commercial collection and sales to be recorded), which should be backed by resources to implement and enforce licensing agreements.

One issue not covered above is the impact of changing coastal structures on sediment transport on the shore, by siltation of rocky shores or baitworm beds, habitat loss and change, and loss of bait stocks. This was a concern raised by several anglers and commercial collectors, but is outside the scope of this project.

Mitigation of these effects, other than as indicated in the preceding sections, is possible to some extent through existing codes of conduct for bait collection, although unfortunately these are sometimes ignored by a significant number of collectors. Bag limits have been attempted, with limited success, to reduce effort and hence environmental impacts. In a few cases, zonation of incompatible activities has been introduced, either under voluntary agreement or backed by legislation. A number of examples of management to mitigate the impact of shoreline species collection are presented in Appendix (Case studies).

Artificial culture using local brood stock may prove to be an important means of promoting the recovery of over-exploited stocks.

Several individuals consulted during the preparation of this report expressed a wish for a licensing or permit system to be introduced for the regulation of commercial bait collection and resale, similar to that in place in Maine (see case study in Appendix II). Such a system would require retail outlets to record the license details of all bait collectors from whom bait was purchased, and the quantities, species and origins of the bait. The benefit of such a system would be the protection of bait stocks for anglers and professional bait collectors from unregistered, unemployed bait diggers. (The latter are thought to be the source of much of the damage to bait beds.) Licensing would also offer improved potential for the assessment and regulation of commercial collection within the area, and the promotion to anglers of codes of conduct for bait collection.

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