Photo: Graham Murrell
Since the early 1990s, Hupacasath First Nation has worked collaboratively with Fisheries and Oceans Canada (DFO) on managing salmon returns to the Great Central and Sproat Lake systems. Over the years, this work has included both juvenile salmon outmigration and adult salmon escapement monitoring. This first of a two-part series explores how Hupacasath Fisheries monitors out-migrating juvenile hissit (sockeye salmon in fresh water).
“Great Central and Sproat Lake sockeye are the two primary stocks we are monitoring,” said Graham Murrell, Hupacasath Fisheries Manager/Biologist, driving to the Sproat River on a drizzly day in late May.
Murrell and his crew, which currently consists of three fisheries technicians, Leon Lauder, Cameron Tatoosh and Lesley Lauder, are working in multiple ways to provide information that is critical to ensuring neither Great Central nor Sproat Lake stocks are overharvested.
These two stocks return via the Somass River and are important to Hupacasath First Nation as they provide one of the largest Food and Ceremonial and economic fishery opportunities in B.C.
The crew conducts acoustic trawl surveys, plankton tows and water quality sampling to assess ecosystem productivity, as well as the number of juvenile hissit nursing in the lakes. The hissit fry tend to spend one to two years in lakes, before migrating to sea.
“It started in Great Central,” said Murrell. “We go out several times per year at strategic times – DFO has a fertilization program on Great Central Lake, so we try to do it before they start fertilizing, during and after.”
Water quality testing assesses chlorophyll-a, nitrate, nitrite and phosphorus concentrations in the lake. Plankton tows are important because zooplankton are the primary food source for hissit, so their abundance, variety and size are important to keep an eye on.
For the acoustic surveys, Hupacasath invested in a BioSonics echo sounder for fisheries applications, which Murrell describes humorously as a “fancy fish finder.” The echo sounder uses scientifically calibrated hydroacoustic technology to capture data on the number of juvenile hissit in a lake and can generate incredibly detailed information like the exact size of a fish.
The crew conducts transects (sections through which observations are made) with the echo sounder and performs trawls in conjunction with the echo sounder work, to be able to see what they are counting.
For the trawls, technicians use a seven-meter by three-meter net to fish at various depths, ranging from 15 to 50 metres. They assess the fish species they have caught (some might be hissit, others may be stickleback, for example), and sample hissit for length, weight and age. Trawls are conducted at night, throughout the winter season.
“Since 2016, the Hupacasath have led the field activities around the acoustic trawl surveys in sockeye nursery lakes both within and outside their traditional territory in South Coast,” said Pieter Van Will, Program Head, WCVI Salmon Stock Assessment with DFO.
Van Will added that, “Working closely with DFO South Coast staff and other local groups and Nations, they have developed a well-run program that contributes to the understanding of sockeye stocks all over the South Coast Area.”
In the spring, Hupacasath Fisheries monitors juvenile hissit outmigration from the lakes, trapping at Robertson Creek and using a Rotary Screw Trap (RST) on the Sproat River.
An RST consists of a large cone suspended between two floating pontoons. River flow rotates the cone and captures downstream migrating fish, leading them into a holding tank at the back of the trap.
The trap (which is now in its second year of use) is installed in mid-April and removed in mid-June. Over those two months, Hupacasath’s technicians monitor it seven days per week, counting and identifying every single fish caught in the trap and sampling a target of 100 fish, three times per week. The fish that are not sampled have bulk weights taken, to generate an average of all the fish weights, and are then released back into the water.
The trap captured 3000 fish the first day it was installed.
“The primary goal is to get an index of what’s coming out,” said Murrell, standing down river from the RST as a light drizzle continued to fall, “but more so, it’s about the condition of the fish as they leave the lake since it’s an indicator of the number of adults that will be returning.”
Hupacasath Fisheries would like to recognize the valuable work Tony Tatoosh contributed to the nation’s fisheries programs over the years, and to acknowledge his recent death. Tatoosh spent considerable time working on juvenile salmon monitoring, and he will be greatly missed.