The pre-fishery abundance is expected to show a minor decline in 2021 and 2022, followed by a gradual increase in line with the projected smolt production. Therefore, with stable fishing mor-tality, a somewhat smaller catch would be caught in 2021-2022 than before or after these years.
Out of the 17 analytically assessed stocks, three (Lögdeälven in AU 2, Ljungan in AU 3, and Emån in AU 4) were below their Rlim in the year 2020 (Table 4.2.3.4a). Results from the stock projections indicate, however, that exploitation similar to the current realized total catch (most similar to scenario 4) will result in either a maintained or positive trend in status for almost all AU 1–4 stocks (Section 4.3.2). Positive or maintained trends in the status of the AU 1-3 stocks have been seen already in the past years (e.g. Figure 4.3.2.5a–e), apparently due to the gradually decreased overall exploitation (Figure 4.2.3.10). The development of a few river stocks, in particular
Vindelälven and Ljungan, is expected to show a somewhat delayed and slower increase due to disease problems in recent years. For Vindelälven, however, two years of increased numbers of returning MSW females indicate that the health situation in this river may be improving.
All the AU 1–4 stocks are predicted to reach >50% of their Rlim in the scenarios 1–3 and 7–10 (Table 4.3.2.2). In other words, a total catch of at least 50 000 (scen 3) but less than 100 000 (scen 4) could be harvested in 2022 with the current fishing pattern to allow all the AU 1–4 stocks to reach their Rlim in the 2025/2026 smolt production. However, the current analytical assessment does not include the AU 5 stocks, for which sea migrations are restricted to the Main Basin (and partly the Gulf of Finland; see Section 4.5.3.1). Most of the wild stocks in this AU are considered to currently be below Rlim, according to expert based elicitations. Analyses performed in 2020 (ICES, 2020b,c) indicated that maintaining a mixed-stock fishery in the Main Basin would likely negatively affect the recovery of these weak wild stocks.
According to new scenarios added this year (7–10), evaluating consequences of a sea fishery con-fined to Åland Sea and Gulf of Bothnia where only AU 1–3 salmon are harvested during their spawning migration, up to 75 000 salmon could be harvested. Under this exploitation rate and a fishing pattern with no Main Basin offshore fisheries, Rlim is expected to be reached in the 2025/2026 for all the analytically assessed stocks (AU 1–4). Such a change in the sea fishery would also increase the protection of the weakest AU 5 stocks.
As observed in earlier assessments, projections under different exploitation rates (+/-50 000 salmon compared to the approximate current level of removal) indicate that such changes in the sea fishery are not expected to result in large changes on the status development of the AU 1–4 stocks, with differences mainly manifesting for weak stocks. This further indicates that fishing mortality is currently at a relatively low level in comparison to other (natural) sources of mortal-ity affecting the stock development. Obviously, probabilities to reach the smolt production tar-gets are higher for scenarios with lower exploitation, but differences between scenarios are rela-tively small except for the ones with a drastically reduced or increased fishing (i.e. scenarios 1, 2 and 6).
Although the AU 5 stocks are not analytically assessed, data on recruitment combined with ex-pert evaluations on production potential indicate no obvious recovery; most of these stocks are currently (year 2020) believed to be far below their MSY-level and most of them are also likely below their Rlim. AU 5 stocks have not generally responded positively to previous reductions in fisheries exploitation, although indications exist about positive effects of temporally increasing overall sea survival (survival from both the natural and fishing induced mortalities) on the re-cruitment among these stocks (ICES, 2020b). AU 5 stocks are exploited in the Main Basin by offshore commercial and recreational fisheries and in rivers by angling, indicating that current exploitation and natural mortality rates (at sea and/or in freshwater) has not allowed for their recovery. One management option to assist the recovery of the AU 5 stocks is to reduce or phase out the Main Basin offshore fisheries (as indirectly seen for AU 4 stocks, with similar migration pattern at sea, in the scenarios 7–10). As discussed above, however, several environmental factors acting during the freshwater phase are believed to affect the development of the AU 5 salmon stocks negatively in addition to sea fishing. Therefore it should be noted, that even without any fishery it may still take considerable time (several salmon generations) until the currently weak-est river stocks will recover.
In contrast to AU 5 stocks, wild AU 6 stocks have shown a positive development in recent years.
The stocks of Kunda and Keila are with high certainty above their MSY level (considering that their current smolt production is at or near 100% of their expert elicited PSPC), whereas the stock status of Vasalemma is rapidly increasing. This indicates that the current exploitation level al-lows a successful recovery of the AU 6 stocks.
Following a temporary and modest increase in M74 in recent years, this mortality factor has again decreased to a very low level. Another factor influencing stock development is the health problem affecting adults that have been observed in certain rivers since 2014 (Sections 3.4.4 and 4.4.1). If these health-related problems should prevail or increase further this may result in de-creased status, particularly for weaker stocks, as well as reduced fishing possibilities, and may easily counteract any positive effects of e.g. good post-smolt survival.
For some weak stocks, additional measures (on top of restrictions through the TAC system) may need to be implemented on the national level to increase the number of spawners, for example by reducing fisheries in rivers or coastal areas where these stocks are currently harvested. For instance, fishing restrictions have been enforced in Vindelälven and Ljungan due to health prob-lems among ascending adults in recent years. Similarly, in Emån and in the recently appointed wild salmon rivers Testeboån and Kågeälven, a fishing ban on salmon has prevailed for many years to increase the recovery rate of these river stocks. A comparison of scenarios 1 (no fishing at all) and 2 (only river fishing allowed) illustrates the positive effects of river fishing regulations.
Measures focused on the freshwater environment, such as work to improve river habitats and migration possibilities, may also be necessary. Thus, special actions directed to the weakest stocks which are not only fishery-related ones are likely required at any advised TAC level, es-pecially in AU 5 but also for a few weak rivers in other AUs, to enable these stocks to recover.
Such work is already ongoing in several countries (see Chapters 2 and 3).
Several of the northern stocks are assessed to be close to or above the MSY-level, and the surplus produced by these stronger stocks could in theory be directed towards stock-specific fisheries.
However, the current management system, with a single TAC for SD 22–31 that is set at a rela-tively low level (from a historical perspective) to safeguard weaker salmon stocks, prevents much of this surplus to be utilised by the commercial sea fishery. Similarly, a large proportion of reared salmon cannot be utilised today because reared salmon is included in the same TAC as wild salmon. Some of the advantages of changing the current management system can be seen in scenarios 7–10, in which the exploitation is focused on reared salmon and the strongest and largest wild stocks in AU 1–3, while the harvesting of the weakest stocks which are located in AU 4–5 is kept close to zero (at much lower levels as compared to under the current fishing pattern; scenarios 3–6).
Consequently, Baltic salmon fisheries management could be developed to become more stock-specific, by implementing more flexible systems for the regulation of fisheries with the aim of steering exploitation towards harvesting of reared salmon and stronger wild stocks and avoiding weak ones. This could be achieved through spatial management, e.g. by implementing area-spe-cific quotas and/or exclusion of certain single-stock fisheries from the quota system (such as fish-eries in estuaries of rivers with reared stocks). Integration of genetic data into population dy-namics models can provide information about stock-specific abundance patterns and harvest rates in time and space, allowing evaluation of spatio-temporal management measures. This creates the potential to move towards stock-specific management whilst maintaining some level of catches in mixed-stock fisheries, since fishing mortality can be directed towards certain stocks (and away from others) using knowledge of stock-specific migration patterns. Such tools are now available and have been applied to the coastal fisheries in Finland and Sweden (Section 4.5.3.2);
these tools could be adapted to form part of the WGBAST assessment framework in the future.
In contrast, the increasing recreational trolling in Main Basin is a true mixed-stock fishery where fully stock-specific harvesting is not possible. Regulations that only allow the landing of fin-clipped (reared) salmon, such as has been implemented in Sweden since 2013, may reduce fish-ing mortality of wild stocks by trollfish-ing if the post-release mortality is relatively low.
As outlined in Section 4.5, the current management of Baltic salmon lacks specific ‘rules’ or guidelines for how fast (within which time frames) weak salmon stocks should recover, and what
proportion of all stocks should have obtained their management goal within a certain time.
Therefore, under current conditions with only TAC regulated commercial sea fisheries and river stocks with varying status, any catch advice for the mixed-stock fishery on Baltic salmon will be associated with some degree of subjective consideration of trade-offs. Sustainable management of Baltic salmon and its mixed-stock fisheries, which accounts for both conservation needs and exploitation possibilities, requires that management accounts for the above and other aspects or trade-offs discussed in Section 4.5. A clarified framework on how to manage Baltic salmon, e.g.
formulated within a multiannual management plan, would also be beneficial for the biological advice process related to this species.