Sea Lion Exclusion Devices
A how-to guide for commercial and recreational fishers
Sea Lion Exclusion Devices (SLEDs) must be fitted in all rock lobster pots (commercial and recreational) used in the identified SLED zone for the 2006/07 fishing season and following seasons. This guide is intended to assist rock lobster fishers with the correct installation of SLEDs in their pots.
The background to SLEDs
A small population of the vulnerable Australian sea lion lives along the mid-west coast of Western Australia. This population overlaps the rich fishing grounds for the western rock lobster and interactions between sea lions and rock lobster pots have occurred over many years. However, small sea lion pups can become trapped in pots and drown. All of the recorded deaths have been in less than 20 metres of water between Freshwater Point and Wedge Island.
Sea lions are slow to breed, females only have one pup every 18 months, and they return to the same sites to breed rather than colonising new areas. This makes small local populations very vulnerable so seal pup drownings in lobster pots need to be prevented.
Australian sea lions are listed as “vulnerable” under the Environmental Protection and Biodiversity Conservation Act 1999 and “specially protected” under the Wildlife Conservation Act 1950. There is an obligation for the West Coast Rock Lobster Fishery and its managers to address this fishing-related mortality issue and it is also a requirement for continued Marine Stewardship Council certification of the fishery.
Research and development history
To develop the best possible way to eliminate the incidental mortality of sea lions in rock lobster pots off the west coast, the Department of Fisheries and the Western Australian Fishing Industry Council established the Sea Lion Scientific Reference Group. High priority was given to research projects that would lead to the introduction of an effective SLED into the fishery.
The group recognised the importance of gaining industry support for the use of SLEDs in order to maximise the effectivness of this initative. The best way to achieve this was to demonstrate that the SLEDs did not reduce the catch of legal size rock lobster.
Extensive trials of the SLEDs were carried out, with the dual objective of testing their effectiveness at keeping sea lions out of pots while also measuring the effect on rock lobster catch rates. A scientific report has detailed the results of several SLED designs.
The best option was found to be an upright bolt fitted to the base and rising towards or to the neck of the pot. The device is simple, relatively cheap and stops sea lion pups entering the pot but does not restrict the pot's ability to catch rock lobsters. The best configuration is to have the bolt set so it sits 20mm below the neck of the pot.
A second type of device, in the form of a batten across the neck of the pot, will keep out sea lion pups, but may have some effect on the lobster catch. Because it is simple to fit and remove, it is preferred by some fishers, so a choice of devices will be allowed.
Measuring and Compliance of SLEDS
Use a SLED gauge to ascertain if a device is compliant
The Department has developed a free SLED gauge to help operators to check their own gear and ensure that it complies with SLED rules. Fisheries and Marine Officers will also be using these gauges in their normal surveillance activities.
- For the purposes of practical field compliance, a moulded/ stamped ball of 132mm diameter will be available free to rock lobster fishers to test the distance from the internal SLED to the bottom of the neck.
- Measurement of round red neck (and black neck) pots is by unforced use of the ball to check the diagonal SLED neck distance.
- Measurement of square necks (finger neck pots) is by unforced use of the ball to check the diagonal distance at each of the four midpoints of the neck.
- The principles of measurement for round red neck and square neck pots will apply to other neck variations in use.
- Measurement of a pot fitted with an external SLED (batten across the neck) will be with the 132mm ball, such that it does not exceed that measurement.
Recreational fishers fishing in the identified area can get their free SLED gauge and SLED from participating Mid-West fishing tackle stores and Department of Fisheries regional offices.
Recommended guide for bolt SLED fixing
Figure 1. Calculated maximum distance (A) between the bottom of the pot neck and the centre of the bolt SLED to achieve proper operation of SLED
The dimensions of pot necks vary significantly, depending on the type of pot being used. Hence the distance of the bolt below the bottom of the neck necessary to correctly fit SLEDs will also vary (see figure 1). The table below shows the dimensions of the bottom of different neck types in mm (i.e. diameter of a round neck or longest side of a square/rectangle neck) and the maximum distance the bolt would need to be set below the bottom of the neck to achieve the maximum allowable SLED distance of 132mm.
Given the difficulty of determining precise measurements especially in the field, the table should be used as a guide only and operators are advised to always determine SLED compliance using the 132mm SLED gauge.
| Maximum Terminal Neck Opening (mm) 132mm SLED |
Vertical distance -A (see Figure 1) |
|---|---|
| 160 | 105 |
| 162 | 104 |
| 164 | 103 |
| 165 | 103 |
| 166 | 102 |
| 168 | 102 |
| 170 | 101 |
| 172 | 100 |
| 174 | 99 |
| 175 | 99 |
| 176 | 98 |
| 178 | 97 |
| 180 | 96 |
| 182 | 95 |
| 184 | 94 |
| 185 | 94 |
| 186 | 93 |
| 188 | 93 |
| 190 | 91 |
| 192 | 90 |
| 194 | 89 |
| 195 | 89 |
| 196 | 88 |
| 198 | 87 |
| 200 | 86 |
| 202 | 85 |
| 204 | 84 |
| 205 | 83 |
| 206 | 82 |
| 208 | 81 |
| 210 | 80 |
| 212 | 78 |
| 214 | 77 |
| 215 | 76 |
| 216 | 76 |
| 218 | 74 |
| 220 | 73 |
| 222 | 71 |
| 224 | 70 |
| 225 | 69 |
| 226 | 68 |
| 228 | 66 |
| 230 | 65 |
| 232 | 63 |
| 234 | 61 |
| 235 | 60 |
| 236 | 59 |
| 238 | 57 |
| 240 | 55 |
| 242 | 53 |
| 244 | 50 |
| 245 | 49 |
| 246 | 48 |
| 247 | 46 |
| 248 | 45 |
| 249 | 44 |
| 250 | 42 |
| 251 | 41 |
| 252 | 39 |
| 253 | 38 |
| 254 | 36 |
| 255 | 34 |
| 256 | 32 |
| 257 | 30 |
| 258 | 28 |
| 260 | 23 |
SLED zones map
All rock lobster pots (commercial and recreational) used in the zone below must have an approved SLED fitted.
SLED zone: A line commencing at (1) the intersection of the high water mark on the coastline of Western Australia and 30º 51.06' south latitude (south of Wedge Island); thence west along the parallel to its intersection with (2) 115º 10.32' east longitude; thence north north westerly along the geodesic to the point of (3) 30º 30.54' south latitude and 115º 0.06' east longitude; thence generally northerly along the geodesic to the point of (4) 30º 25.02' south latitude and 114º 58.5' east longitude; thence generally northerly along the geodesic to the point of (5) 30º 12.42' south latitude and 114º 57.0' east longitude; thence generally northerly along the geodesic to the point of (6) 30º 4.2' south latitude and 114º 54.42' east longitude; thence generally northerly along the geodesic to the point of (7) 29º 54.96' south latitude and 114º 53.52' east longitude; thence north north westerly along the geodesic to the point of (8) 29º 47.82' south latitude and 114º 50.64' east longitude; thence north easterly along the geodesic to the point of (9) 29º 44.28' south latitude and 114º 52.2' east longitude; thence generally northerly along the geodesic to the point of (10) 29º 35.16' south latitude and 114º 53.58' east longitude; thence east along the parallel to its intersection with (11) the high water mark on the coastline of Western Australia (north of Freshwater Point); thence generally southerly along the high water mark to the commencement point.
Approved SLEDS
(1) Internal SLED
A SLED is achieved by the fixing of a rigid, non-flexible piece of material rising vertically from the base of the pot to a height that ensures the diagonal distance to the neck from the top centre of the internal SLED is no greater than 132mm. The diagonal distance is to be measured to the edge of the neck in any direction in a round neck, and to the midpoint of the four sides in a square or rectangular neck.
Dimensions of internal SLED
The internal SLED must be a minimum of 10mm in diameter and the top of the internal SLED must be a minimum of 10mm and a maximum of 30mm in diameter.
(2) External SLED
A SLED is achieved by fixing a rigid, non-flexible material across the top of the neck that ensures that the gap from the edge of the external SLED to either side of the top of the neck is no greater than 132mm.
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