ADFG Releases 2020 Southeast Pink Salmon Forecast

Alaska Department of Fish and Game released its 2020 Southeast Alaska pink salmon forecast earlier this weer. Here are some of the highlights:

The 2020 harvest forecast of 12 million pink salmon is approximately one third of the recent 10-year average harvest of 35
million pink salmon. A harvest near this forecast would also be approximately 60% of the average even-year harvest since
2006. The 2019 peak June–July juvenile pink salmon index value (1.20) ranked 21st out of the 23 years that SECM
information has been collected. Pink salmon harvests associated with juvenile indices below a value of 2.0 have ranged
from 8 to 37 million fish (mean=21 million fish).

The low juvenile abundance index in 2019 was not unexpected. Pink salmon escapements in the parent year (2018) were
very poor throughout northern Southeast Alaska inside waters and the escapement goal was not met in that subregion, which
may have resulted in below optimal egg deposition. Escapement and harvest of pink salmon in the Northern Southeast Inside
subregion have been very poor since 2012 and the 2020 forecast indicates this pattern is likely to continue.

Pink salmon escapement goals for the Southern Southeast and Northern Southeast Outside subregions were met in 2018, but harvests
were well below average. The low juvenile abundance index in 2019 may also indicate that brood year 2018 pink salmon
experienced poor freshwater and/or early marine survival.

It is possible that drought conditions present in Southeast Alaska
from the parent year 2018 spawn through the spring of 2019 reduced spawning success or negatively impacted overwinter
survival of developing juvenile salmon, but the exact reasons for the low juvenile abundance are not known. Juvenile pink
salmon caught in the 2019 SECM survey trawls, however, were among the largest (in length) in the 23-year time series
(Figure 3) and were in good condition, which indicates favorable nearshore marine conditions in the spring. The size of
juvenile pink salmon was similar to the large size of juveniles observed during the marine heat wave of 2014–2016 (Figure
3) and returns from those juvenile years were all below average.

Like many recent years, a potential source of uncertainty regarding the 2020 pink salmon return is the anomalously warm
sea surface temperatures in the Gulf of Alaska in 2019. Warm temperatures that persisted throughout the Gulf of Alaska
from fall 2013 through much of 2016 (Bond et al. 2015; Di Lorenzo and Mantua 2016; Walsh et al. 2018) returned in 2018
and strengthened in 2019. Compared to sea surface temperatures since 1997, when NOAA first started the SECM project,
surface temperatures in the Gulf of Alaska in 2019, immediately offshore of Southeast Alaska, were the warmest of the time
series in July, the 4th warmest in August, and 3rd warmest in September 

Sea surface temperatures were well above average
across the entire Gulf of Alaska during that time. Pink salmon that went to sea from 2014 to 2018 returned in numbers
below expectation and below recent odd- and even-year averages. The impact of warm sea surface temperatures on the
survival of pink salmon that went to sea in 2019 is unknown and adds uncertainty to the forecast.