November 27, 2008

DFO Explanation of Data and Science Pertaining to Point System (Lobster Management)

Data sources and calculations from Science
 
PRODUCTIVITY
Minimum Legal Size
 
Data source: The Size at the Onset of Maturity (SOM) was established based on ovaries condition and cement glands for several locations throughout the sGSL, from 1984 to 2006.
  • The SOM represents the carapace length (CL) at which females reach sexual maturity and produce eggs for the first time.
  • The first FRCC report (1995) mentioned that one of the key elements to achieve a healthy fishery is a good egg production by allowing females to spawn before being captured. In their second report the FRCC (2007) suggested to use the size at 50% SOM (SOM50) to establish the Minimum Legal Size (MLS) to protect first spawners.
  • Having a MLS larger than the SOM50 will increase productivity in a given area as more first spawners will be protected from exploitation and will be able to produce at least once batch of eggs before entering the fishery.
  • Points are attributed according to maturity curves. One point for a MLS 1 mm above the SOM50 and 5 points for the MLS established at SOM90 (allowing for all females to spawn at least once before entering the fishery).
 
 
 Data sources and calculations from Science
 
 
REDUCING EFFORT
Rating System
 
The rating system is based on the exploitation rate (ER) estimated to be around 70% in all LFAs except for LFA 26A were it is around 65%. From the basic objective of reducing ER by 10% we obtain the following numbers:
 
            70% * 10% = 7% ER reduction all LFAs except 26A
            65% * 10% = 6.5% ER reduction in LFA 26A
 
The ER reduction is based on a 10 points rating system:
 
All LFAs with ER at 70%
LFA 26A with ER at 65%
Rating
% of reduction
% of reduction
New ER%
1
0.7
69.3
0.65
64.4
2
1.4
68.6
1.3
63.7
3
2.1
67.9
2.0
63.1
4
2.8
67.2
2.6
62.4
5
3.5
66.5
3.3
61.8
6
4.2
65.8
3.9
61.1
7
4.9
65.1
4.6
60.5
8
5.6
64.4
5.2
59.8
9
6.3
63.7
5.9
59.2
10
7.0
63.0
6.5
58.5
 
Number of Days Fished at the End of the Season
 
Data source: catch statistics from fisher-index logbooks compiled from 2001 to 2005.
·        The cumulative five-year daily average landings were transformed to cumulative ER where the last day of the season represents 70% or 65% according to the LFA.
·        From the last day of the fishing season, the rating system is applied to the ER reached that day up until a maximum value of 10 points.
 
Number of Traps per Harvester
 
Data source: at-sea sampling program, from 2000 to 2006 (depending on data availability).
  • The average percentage of empty traps (i.e., number of traps without commercial size lobsters divided by the total number of traps sampled) was calculated by combining all data from samples collected between 2000 and 2006 in each region.
  • Based on the maximum trap allocation per LFA (2005 as the reference year) and the average percentage of empty traps, the number of “effective” traps was calculated (annual trap allocation minus the number of empty traps). That number served as the baseline for the 10% ER reduction.
  • The rating system was similar to the number of days fished at the end of the season using the number of “efficient” trap as the reference starting point for ER reduction.  Minimum Number of Traps per Line
 
Data source: observation and traditional knowledge.
·        Reducing lobster catchability could be achieved by limiting the quantity of traps on reefs.
·        Each trap from single trap drops could be placed directly on a lobster reef compared to traps attached on a line (i.e., lower probability of a single trap directly on a lobster reef).
·        Point rating for that effort reduction measure was established between 1 and 3: 1 point for a minimum of 3 traps per line (between 3 and 5 traps per line), 2 points for 6 traps per line (between 6 and 9) and 3 points for 10 traps per line or more. It is recognized that in some regions, due to security reason (i.e., smaller boats), the maximum number of traps per line would be 3.
 
Maximum Entrance Diameter (Hoop Size)
 
Data source: trap selectivity study in 2004 in Cribbon’s Point (NS). Five ring diameters were tested: 4”1/2, 5”, 5”1/2, 6”, and 8”.
·        The study results indicate that traps equipped with larger ring diameter will tend to catch larger lobsters (>115 mm CL) given their availability. Hence, limiting the ring diameter could be an indirect method for reducing the catchability of large lobsters.
·        Point rating was 1 for 6” and 51/2” entrance rings (similar results for the size of animals captured during the study) and 2 for entrance rings of 5” or less.
 
Maximum Carapace Size
 
Data source: at-sea sampling, observation, traditional knowledge.
  • Maximum carapace size cannot be calculated only from at-sea sampling data because those might not reflect the actual proportion of large lobsters because original sampling protocols were not designed for that goal.
  • Implementing a maximum carapace size for both male and female lobsters is a direct measure of effort reduction because part of the population will no longer be available to the fishery.
  • Point rating was 1 for a maximum carapace size for male and female of 125 mm, 2 for 120 mm, and 3 for 115 mm.
 

 
 
 
 
 

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