Assesment of the lumpfish population in Iceland
The lumpfish population in Iceland is assessed 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.
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 lumpfish caught during the survey. One male and female from each station is weighed, the maturity status determined, 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, it does not give information on the absolute size of the population. Only a small number of males are caught during the survey and thus the survey is not considered to give a good indication of changes in the abundance of males.
Each boat which participates in the fishery must submit a logbook detailing the number of nets hauled on each fishing trip, the soak time (the length of time they have been in the water since they were last hauled) of the nets and the weight of lumpish caught. This can be used to calculate CPUE (Catch Per Unit Effort) (Figure 2). Fish caught by the fishery are also measured and weighed to give an information on the size of the fish caught (Figure 3).
An index of total effort in the fishery (Figure 4) is estimated by using the formula
$$\textrm{effort} = \frac{\textrm{total catch from the fishery}}{\textrm{average CPUE}}$$
Other measurements of effort are also monitored including the total number of boats which take part in the fishery and the number of days each boat spends fishing.
As the total size of the population is unknown, a relative index of fishing mortality is calculated (Fproxy) using the formula
$$F{proxy} = \frac{total\ catch\ from\ the\ fishery}{Biomass\ index}$$
The recommended total catch of female lumpfish is based upon maintaining Fproxy below 0.75, this is based upon recent fishing experience from 2008-2020 which suggests that the population can withstand a fishing mortality at this level (Figure 5). There are a number of safeguards in place to protect the population if the biomass begins to decrease. If the population biomass falls below a specific level, termed Btrigger, then the recommended target fishing mortality is reduced in proportion to the reduction below Btrigger (Figure 6). If the biomass falls below Blim, then the recommended TAC is zero. The recommended TAC is also based upon the preceding and current years biomass index which have a weighting of 30 and 70% respectively.
The total catch has been below the recommended TAC in 4 out of the 8 years since it was fully implemented in 2013 and Fproxy has been below Target Fproxy in 6 of the previous 8 years (Figure 5).
