Sockeye Math Kenai River Style

The salmon fisheries in Upper Cook Inlet have always been volatile and contentious, but the 2012 season has raised the bar on “volatile” because of a record low run of late-run king salmon bound back to the Kenai River. The Alaska Department of Fish and Game (ADFG) does not anticipate achieving the minimum objective for spawning escapement of late-run king salmon in the Kenai.

The movement of sockeye salmon from the marine waters of Upper Cook Inlet to the Kenai River is now peaking. The sport fishery for late-run kings is closed for the season. The commercial east side set net fishery is closed through the end of July and the commercial drift fleet is going gangbusters trying to take up the slack in harvest potential on Kenai bound sockeye salmon created by the commercial set net closure. The personal use fishery is now open 24 hours per day until 11:59 p.m. Tuesday, July 31 and the daily bag for the sport fishery has been increased from three to six fish with twelve in possession.

We are going to hear a lot of numbers in the coming few days as the sockeye run makes its move toward the rivers. To have a basic understanding of what is going on it is important to know what the numbers refer to and which has the most bearing on management decisions.

Sockeye salmon are counted in the Kenai River at River Mile 19 with a Didson sonar unit similar to the experimental Didson unit (located at River Mile 8.6) used to assess king salmon abundance. The Kenai River Late-run Sockeye Salmon Management Plan states that the commercial, sport, and personal use fisheries shall be managed to meet an optimal escapement goal (OEG) of 700,000 to 1,400,000 late-run sockeye salmon. Additionally, the plan directs ADFG to achieve in-river goals as established by the Alaska Board of Fisheries (BOF) as measured at the sonar counter , and also distribute the escapement of sockeye salmon evenly within the OEG range, in proportion to the run size.

The in-river goal is comprised of fish destined for the spawning grounds and fish anticipated to be harvested in the sport fishery above Mile 19. This year the run return was forecast at 4 million fish, which puts the return in the middle tier, between 2.3 and 4.6 million. The in-river goal for this tier is 1,000,000 – 1,200,000 sonar counts. This number can change if the total return is smaller than 2.3 million or larger than 4.6 million. ADFG will make any necessary adjustments to the total return of sockeye salmon to the Kenai after the mid-point in the return, typically by July 24. For example, in 2011 the return was forecast at 3.9 million, but was upgraded to over 4.6 million at the mid-point of the return, with a final tally of 5.9 million.

And now some sockeye math – Kenai River style

The commercial harvest, the harvest in the personal use fishery and a portion of the sport harvest occur downstream of Mile 19 sonar counter. In 2011 the commercial harvest of Kenai River sockeye was about 3,700,000, the personal use harvest about 500,000 and the sport harvest downstream of Mile 19 about 100,000. In 2011 these combined harvests totaled about 4.3 million sockeye. The Mile 19 sonar counter tallied about 1.6 million sockeye, which when added to the 4.3 million in harvest below the sonar makes for a total return of 5.9 million late-run sockeye of Kenai River origin.

However, the Mile 19 sonar counter does not account for harvests by in-river anglers upstream of the counter – as determined by the ADFG statewide harvest survey (SWHS). In 2011 the SWHS indicated harvests by in-river anglers above Mile 19 at 350,000. To get the escapement of spawners, subtract the harvest by sport anglers (350,000) from Mile 19 sonar count (1,600,000) to get the final estimate of escapement – 1,250,000 sockeye spawners in 2011.

The three in-river goals for late-run sockeye salmon of Kenai River origin are based upon abundance. The in-river goal is an allocative management objective since it is a blend of fish destined for both harvest and escapement. For returns less than 2.3 million, the in-river goal is 900,000 to 1,100,000; for runs between 2.3 and 4.6 million, the in-river goal is 1,000,000 to 1,200,000; and for returns greater than 4.6 million, the in-river goal is 1,100,000 – 1,350,000. For 2011, with a run-return greater than 4.6 million, the in-river goal was 1.1 to 1.35 million and the final escapement fell within that range at 1.25 million.

The OEG for the Kenai River is a sustainable biological goal that also takes also takes into account the best available science and the difficulty inherent in management. The number of sockeye desired past the mile 19 sonar counter is 700,000 – 1,400,000 fish, while the sustainable escapement goal (SEG) is to have between 700,000 – 1,200,000 spawners, when in-river harvests by anglers are subtracted from the sonar counts, as shown in the example above.

Escapements for Kenai River late-run sockeye less than 700,000 is considered inadequate and is potentially a long-term conservation concern if occurring on a repeated basis; going above 1,400,000 produces more spawners than is optimal, and is considered a yield concern as it results in lost harvest opportunity, but is not generally considered a conservation concern.

Some claim going over the upper end of the sockeye escapement goal is harmful to future production (the over-escapement “theory,” a discussion for another time). On the Kenai River, sockeye escapements have been as high as two million, yet this has not yet manifested itself in lost production, as the Kenai sockeye have never failed to reproduce at a one to one ratio. Statewide, approximately 50 percent of all sockeye returns exceed the upper end of their escapement goal, 40 percent have spawners within their escapement ranges, and 10 percent fail to meet the lower end of their escapement range.

The bottom line here is that a primary objective for ADFG when managing the Kenai River late-run sockeye fishery is to end the season with a sonar count at Mile 19 between 1,000,000 and 1,200,000. However, the most important objective is the OEG, which is a much wider range of numbers from 700,000 to 1,400,000. Remember that this year with heavy in-river angling activity for sockeyes above Mile 19, an estimated 300,000 to 400,000 sockeye will be removed from the river above the sonar counter. Do the math. A sonar count at the top end of the range will provide for an escapement of only about 950,000. Until we reach a sonar count of 1,750,000 we are still within the desired range of optimal escapements.

The need to restrict fisheries to achieve an adequate level of escapement of late-run king salmon has complicated matters considerably in 2012. With the set net fishery restricted it was important that the harvest potential of the central district drift fleet, the Kenai River personal use fishery and the sport fishery be optimized. ADFG has issued Emergency Orders aimed at harvest optimization by these fisheries.

The remainder of the 2012 season will unfold quickly and it is not unlikely that we will challenge or exceed the upper end of both the in-river goal and the OEG. It is also very likely that in spite of all the restrictions put in place to protect king salmon we will still fall short of the desired minimum escapement for that species. That might just be what success looks like in 2012.

At the end of the day, why does meeting the lower end of the late-run Kenai River king salmon escapement goal take priority over meeting the upper end of the late-run Kenai River sockeye salmon escapement goal? Because exceeding the upper end of the sockeye escapement does not pose a long term conservation issue, whereas not meeting the lower end of king salmon escapement goal does pose a long term conservation issue.

For example, between 2000 and 2010, the upper end of the Kasilof River sockeye salmon escapement goal was exceeded regularly – the result is that the upper end of the Kasilof River escapement goal was raised in 2011 to reflect that larger escapements into the Kasilof produced more fish in the long run. As such, the upper end of the OEG for the Kasilof was raised from 300,000 to 390,000 fish, so that the OEG is now 160,000 to 390,000 Kasilof sockeye. Forty years ago the upper end of the escapement goal for Kenai River sockeye salmon was 250,000. Today, more than a million more sockeye escape into the Kenai River watershed as spawners. This is a very important history lesson that few people remember or speak of and the media do not report.

However, between 2000 and 2010, the lower ends of king salmon escapement goals were not met regularly in numerous Upper Cook Inlet northern district rivers. As a result in 2011 the Alaska Board of Fisheries took the action to close these rivers to sport and commercial harvests of king salmon.

Exceeding the upper end of escapement goals has not closed fisheries in Upper Cook Inlet, whereas not meeting minimum escapement goals has. Therein is the reason why meeting the lower end of the late-run Kenai River king salmon escapement goal takes priority over meeting the upper end of the late-run Kenai River sockeye salmon escapement goal.