Fig 1.
A Barents Sea snow crab vessel (MS North Eastern) on its way to the fishing grounds with the deck full of stacked conical pots (Photo: Opilio AS).
Fig 2.
Comparison of the geometry and dimensions of the standard conical pots (control pots) and moon pots (experimental pots).
The arrows illustrate the distances from the pot’s wall to the bait container.
Fig 3.
Geometry differences between the pots.
(a) Outer profile of the standard conical pot (solid line) and the moon pot (dashed line). (b) Steepness of the outer profile along the path to the pot entrance for each of the pots. (c) Distance to the bait core along the path to the pot entrance for each of the pots.
Table 1.
Mean (SD) mesh opening size, mesh opening angle, and hanging ratio for both types of pots and significance of statistical tests.
Significant values are given in bold.
Table 2.
Individual sets of pots with corresponding start position, depth, soaking time, number of pots used, and the number of snow crabs caught in the different pots used in the analysis.
Fig 4.
Populations caught (first row), catch comparison rates (centre row), and catch ratios (bottom row) for standard pots against moon pots.
In the population plots the black curve represents the population caught in the test pots, and the grey curve represents the raised population caught in the standard pots. The experimental catch comparison rate [according to Eq (1)] is represented by circles. For the modelled catch comparison rate and catch ratio, the full black curve represents the estimated mean curve and the stippled curves represent the 95% confidence intervals. Horizontal dotted curves represent baseline for no effect of change in pot design on catch comparison rate (at 0.5) and catch ratio (at 1.0), respectively.
Table 3.
Catch ratio (CR(w)) (%) and fit statistics obtained for the moon pots versus the standard pots.
CR(w) values that are significantly different from 100% (i.e., those with same fishing efficiency as standard pots) are in bold. Values in brackets represent 95% confidence intervals. DF = degrees of freedom.