Whilst there are relatively low level fisheries along the coasts of both South and North Wales, Cardigan Bay (Cemaes Head to the Llyn Peninsula) fishermen have been prosecuting a fishery for the common prawn (Palaemon serratus) for many years.

The Cardigan Bay fishery has to an extent followed a normal pattern of a poorly managed yet profitable fishery in that initially excellent returns for a small number of vessels operating relatively low numbers of pots has evolved into a free for all with numbers of participating vessels and quantities of gear increasing year on year.

Allied to this increase in effort is an absence of common sense or understanding in relation to long term sustainability with effectively little or no size selectivity, grading or care of the catch in many instances.

With no sense of ownership of the fishery possible within the present legal framework of effectively unrestricted effort allied to an abrogation of responsibility for management and regulation by those authorities who ostensibly have a duty in this area, a free for all mentality becomes extant with the almost inevitable demise of the fishery over time.

This fishery has now reduced to a shadow of its original production quantities and gear numbers continue to increase to offset the reductions in CPUE.

Local fishermen are now looking to their Association and the Federation for a lead in introducing management initiatives in order to save the fishery from collapse and to ensure that emerging Palaemon fisheries in Wales do not go the same way.

At the other end of the supply chain the merchants who purchase the product relate an all too familiar tale of over production, together with little or no grading as well as occasionally high mortality rates resulting in marketing difficulties. Allied to those difficulties is a concern that this species may follow the same story of the brown crab in that an abundant but largely uncontrolled fishery has resulted in poor quality product with relatively high mortality rates being over supplied to the markets and returning the same price to the primary producer as it did 25 years ago.

On the other hand, according to the main buyers, if quality and size can be maximized and the supply regulated then demand and therefore prices will be maintained or even improved.

The general consensus of participants in the recent Cardiff Palaemon workshop, the majority of whom were practicing fishermen, was that whilst it was important that the maximum number of fishermen should benefit from the fisheries around the Welsh coastline, there was an urgent need for effective effort controls to ensure the long term sustainability of the species.

In looking at the following considerations it should be noted that although a great deal of excellent work has been done on this species, mainly by Eoghan Kelly of BIM, there are few certainties in this area of stock analysis. There are however, sufficient data, coupled with the observations of fishermen over a significant time period to provide confidence in suggesting some practical management options. It should also be remembered that byelaws, Statutory Instruments and other regulatory options are not set in stone and that precautionary measures put in place to ensure stock sustainability can be amended in the light of further work.

Some elements of sustainable management need further thought and consideration before we encourage additional controls, initiatives such as pot limits and vessel permit schemes require detailed work before implementation. On the other hand there are a number of fairly straightforward management options that could be introduced, through local Sea Fisheries Committee byelaws or a Statutory Instrument without delay. The following notes are intended to act as a rationale for the introduction of a close season, a minimum landing size, mandatory onboard grading and a minimum mesh size for the end cones of the pots used as interim management measures that the industry might consider as a first step.

Recent work by the Irish Sea Fisheries Board (BIM) has clearly identified a rationale for a closed season to protect the growing stock.

One can see that there is a significant growth spurt at or around week 60 which equates to around the end of June. This growth rate starts to tail off from about week 72. The resultant increase in weight (and therefore profitability) should be protected to ensure the maximum yield per recruit and therefore a close season should be introduced from 1^st May to 1^st October.

There is little doubt that by introducing a close season to procure the optimum weight per recruit that it also maximizes the CPUE for fishermen. A close season should also of course equally affect the non commercial take.

The graph below illustrates the point in that CPUE is at maximum at or around the suggested permitted fishing period.

On the other hand, it is clear from the graph below that there is an unfortunate correlation between the intended fishing effort period to obtain the maximum size and weight of product (as well as to fit in with other fishing targets) and the number of berried hens in the fishery.

It will be vital to introduce effective monitoring of the fishery through both external data collection as well as an efficient, preferably electronic log book scheme so that we can start to gather quantifiable indicators on how the stocks are reacting to effort and management and therefore provide an indication of the direction in which the industry and regulators should proceed.

It is of course important to select the preferred size of Prawn for a number of reasons.

Not only to ensure that sufficient mature prawns are left to provide a source of catch in future years but also to produce a product that is fit for the market and one that the fishermen are providing at the best size which in turn provides the best return for their effort and expenditure for catching them in the first place.

There are a number of options that should be considered and again the work done by Eoghan Kelly as well as that undertaken locally by Ben Fothergill, Development Officer of the Cardigan Bay Fishermen’s Association provide sufficient indicators for us to be able to come to some workable conclusions.

We have already considered the imposition of a close season to allow the species to grow to the optimum size in terms of yield and to protect the growth area in order to provide optimum size at capture. Despite that, there will be a number of prawns attracted to the pots that should not be included in the final catch for obvious reasons, i.e. protection of future breeding stock, maximizing price through the supply of large prawns and balancing supply and demand.

The options for the management of size selectivity are:

It should be noted that no consideration is given to the riddling of catches at the point of sale to merchants as that would result in an extremely high mortality rate for no benefit to the supply chain overall.

Amongst the range of studies done in this area, a number of different parameters are used to identify prawn size/maturity, i.e. carapace length, total length, weight, age and carapace width. Suffice it to say that irrespective of the measurement used, the outcome in terms of the preferred management remains the same.

In general terms the species becomes sexually mature at approximately 70mm – 80mm, it lives for about three years and in any population structure one will find 2 or 3 distinct age groups.

As already mentioned, it is important to be able to remove the preferred group, i.e. those that have spawned at least once and provide the maximum yield per recruit to the fisherman, whilst leaving the undersized remainder undamaged to continue the fishery.

From the work done it is clear that the optimum size for capture in order to fulfill all the previously identified parameters is 90mm overall length and that this overall length relates to a carapace width of approximately 9mm.

(Graph for information):

It is generally accepted that one should not take any species unless at least 50% have reached maturity. From the graph above we can see that the absolute minimum carapace length at 50% maturity is 14.55mm which equates to 78mm total length or 3.3 grammes in weight.

We consider as previously stated that a total length of 90mm is the optimum to ensure long term sustainability. This equates to a carapace length of 17mm and a carapace width of 9mm. In order to remove the undersized portion of the catch through riddling, we suggest a grid spacing of 10mm within an obligatory on board riddle. We would also suggest that fishermen make up a chute so that undersized are returned immediately to the sea, preferably slightly under the surface rather collected in a box and subsequently tipped back.

Whilst it may be preferable to await the arrival of EFF support before considering a requirement to increase the size of the mesh in the end cones of the pots there are two primary reasons why we should consider this opportunity now. Firstly regulators would much prefer a complete package of measures in the first phase, rather than having to introduce legislation in a piecemeal fashion. Secondly, from work already completed it is apparent that changing the end cones in pots is neither expensive nor onerous. Changing the cones should take less than twenty minutes per pot and the cost is negligible. If fishermen were required to make this change then it is certainly a task that could be completed before the start of the 2007 season. Additionally, advertising the forthcoming requirement would allow fishermen to specify a larger mesh size from the manufacturers, thereby precluding the need to change end cones on new and replacement pots.

Finally, whilst riddling will remove the majority of undersized from the catch, there are concerns that riddling increases the mortality rate through hauling and the subsequent shock of exposure, physical damage during the handling and riddling phase as well as on the return journey to the seabed.

Bearing in mind the proposed MLS of 90mm overall length then the graph below clearly demonstrates the effects of a range of end cone mesh sizes on the catch size composition.

The second and final graph demonstrates clearly that the inclusion of 14mm mesh end cones increases the average percentage weight of over 90mm prawns in the catch and significantly reduces the by-catch of undersized.

Having concluded the mesh size selectivity trials we are clear that there is a strong argument for the introduction of a 14mm mesh size for both end cones of prawn pots.

For information the study methodology in brief consisted of 2 strings of gear with 18 pots on each string. The 2 strings were shot in the same position (approx. 20 metres apart) and hauled every two weeks, the catch from each pot was put into a separate labelled bags, these bags were returned to the laboratory and frozen.

The samples were later defrosted, weighed and measured. The pots had a range of 5 mesh sizes (Treatments) 9mm, 14mm, 18mm, 18mm(big) [the whole pot rather than just the two ends] and 22mm compared against an unmodified control (standard Roscoff pot)

Each group of 6 pots represented an individual experiment, Pots with different treatments were random within each group, Each string had 3 groups of pots (3 replicates).

The rationale for the increase is thus:

The author has attempted to include sufficient information and data within this paper to provide a clear and unequivocal rationale for more effective management of the fishery but not so much as to confuse the arguments. There is a wealth of information available to managers and practitioners to give further support to the aforementioned proposals. Please feel free to request said data from the Federation headquarters if you require it.

The interim management options outlined above, of a close season, a mandatory onboard riddle together with a minimum landing size and a mesh size of 14mm in pot ends are considered to provide a straightforward base level of control and protection.

Further work on sustainable management options is ongoing, these options for consideration will include pot limitation, vessel permit schemes, compulsory electronic logbooks and a reduction on the publicly permitted take.

A final thought for regulators is how they can ensure that any and all regulations also relate to the ‘public’ as well as the commercial harvesters.

Jeremy Percy

16^th August 2006

Note: These considerations would not have been possible without the input of the inshore fishermen of Wales in general and Eoghan Kelly and Seamus Breathnach of the Irish Sea Fisheries Board and Ben Fothergill of Cardigan Bay Fishermen’s Association in particular. Much of the data are taken from their recent presentations. We are duly grateful.

Top