Assessment

The lumpfish population in Iceland is assesed on an annual basis to provide advice for the Total Allowable Catch (TAC) for the fishery. This advice is primarily based upon a relative abundance index from the Icelandic spring groundfish survey which takes place each year in February-March. Other data is also taken into consideration including catch and effort data from the fishery and length measurements from the fishery in the previous year.

Figure 1. Distribution of catches from the Icelandic spring groundfish survey in 2018. Red dots show stations where lumpfish was not caught. The size of the circles denotes the total weight of all the lumpfish caught at that station

The Icelandic spring groundfish survey takes place annually and covers the entire shelf area from 50-500m around Iceland (Figure 1). The length is measured and sex determined for all the lumpfish caught during the survey. One male and female from each station is weighted and the otoliths are removed. Using this data, an index of the biomass can be calculated (Figure 2). This is considered to give a good indication of changes in the abundance of female lumpfish over time. However, few males are caught during the survey and thus the survey is not considered to a good indication of changes in the abundance of males.

Figure 2. Biomass index from the Icelandic groundfish survey (black line) and catch per unit effort for the fishery (red line)

Each boat which participates in the fishery must submit a logbook detailing the number of nets hauled each day, soak time and the weight of lumpish caught. This can be used to calculate CPUE (catch per unit effort) (Figure 2).

An index of total effort in the fishery itself is estimated by using the formula

$$\frac{total\ catch\ from\ the\ fishery}{average\ CPUE}$$

Other measurements of effort are also monitored including the total number of boats which take part in the fishery and the total number of fishing days (number of boats * number of days fished by each boat).

Figure 3. Relative fishing effort in the lumpfish fishery between 1985-2017.

As the total size of the population is unknown, a relative index of fishing mortality is calculated (Fproxy) using the formula

$$\frac{Total\ catch\ from\ the\ fishery}{Biomass\ index}$$

The long term management goal is to maintain Fproxy below 0.75, this was estimated as the average fishing mortality between 1985-2011 (Figure 4). To compensate for uncertainty in the estimation of the biomass index, the survey index from the previous year is also taken into account with a weighting of 30% in the calculation for the recommended TAC.

Figure 4. Relative fishing mortality (Fproxy) of the lumpfish population in Iceland from 1985-2018.The Target mortality (red line) and the mean Fproxy between 1985-2011 is shown (black line).

The total catch has been below the recommended TAC in 4 out of the 6 years since it was fully implemented in 2013 and Fproxy has been below Target Fproxy in 5 of the previous 6 years (Figure 4).