NWT RESEARCH DATABASE

Tags: biology, fish sampling, fish, habitat, lake trout

Objective(s): To sample known and newly discovered deepwater (>50 m) habitats southwest of the Narakay Islands and within the McTavish Arm to determine if a deepwater humper or siscowet lake trout form occurs in the Great Bear Lake.

Project Description: The objective of this project is to sample known and newly discovered deepwater (>50 m) habitats southwest of the Narakay Islands and within the McTavish Arm to determine if a deepwater humper or siscowet lake trout form occurs. Data on the occurrence and characteristics of deepwater lake trout forms from Great Bear Lake will fill in gaps in this North American lake trout dataset. Currently it is unknown if deep-dwelling lake trout forms occur in Great Bear Lake. The sampling efforts will be concentrated in deep (>50m), offshore waters that are not targeted by subsistence fisheries or by recreational anglers. The research team proposes to sample the deep waters around the Narakay Islands, Dease Arm (66°43’18N; 120°06’05W) and the eastern side of McTavish Arm extending from the Doghead Peninsula in the north (66°24’19N; 117°54’15W) to the Superstition Islands in the south (65°53’10N; 118°32’24W) between 01 and 20 August, 2012. Plummer’s Arctic Fishing Lodge has agreed to supply accommodations, aircraft, boats, and supplies. The researchers have a working relationship with the lodge and they have supported related previous research efforts. The researcher proposes to use the same sampling methods and approaches that have been used on other lakes and previously on Great Bear Lake in 2004. Each nylon gill net is 30.5 m long and 1.8 m high. Six nets (stretch-mesh sizes: 50.8, 63.5, 76.2, 88.9, 101.6, and 114.3 mm) will be joined together in a 183-m gang and deployed on bottom in depths ranging from 50-200 m. This sampling gear is designed and deployed in a way proven to minimize bycatch (i.e., non-target species and large lake trout); thereby, minimizing non-target fish mortality. Although the team don’t anticipate bycatch, all Arctic grayling Thymallus arcticus, cisco Coregonus artedi, burbot, Lota lota, lake whitefish Coregonus clupeaformis, longnose sucker Catostomus catostomus, and round whitefish Prosopium cylindraceum) will be released live. The target sample combined from the two locations will be 150 deep-water lake trout. This number is based on minimum sample sizes required for genetic and morphometric analyses. To achieve this sample size, the research team intends to set three nets in four or five locations. In 2004, the team made eight sets in water ranging from 40 to 112 m depth and caught between 2 to 20 lake trout per set (average = 13 fish per set). Although the overall lake trout population size in Great Bear Lake is unknown (Howland and Tallman, 2005), the team does not anticipate any negative effects of removing this number of animals from the population. The sample size is well below that collected by DFO during 2000 and 2001 (Howland et al., 2004). Due to the selectivity of this sampling gear, combined with this sampling depths, the research team does not anticipate removing any large, old animals—only one fish >5 kg was caught during this 2004 sampling using the same gear. The fish sampling protocol is designed to maximize the amount of useable biological data obtained from each fish. From all deepwater lake trout morphs and mortalities of non-deepwater lake trout morphs, the research team plans on collecting data on biological characteristics (length and weight), sex and maturity, age and growth (otoliths), food habits, habitat, buoyancy (related to fish lipid content), body fat measure (via a handheld fat meter), body and head morphology, and genetics. Dead cisco will be sampled; a photograph will be taken to analyze body shape and a small fin clip taken for genetic analysis. Live, non-target lake trout forms will also be photographed and a small fin clip will be collected for genetic analysis prior to release. Once data are collected, the team would like to meet with Deline elders to present the data and seek their guidance and suggestions on interpreting the information. In particular, the team would like to understand what is known about different deep-water lake trout forms and if they have been observed elsewhere in the lake. Copies of raw data, research completion reports, and peer-reviewed publications will be submitted to the Great Bear Lake Working Group, the Sahtu Renewable Resources Board, and Deline First Nation. In addition, Tim Edwards, Northern News has agreed to run an article highlighting the research so that it can be disseminated broadly throughout the northern communities. The fieldwork for this study will be conducted from August 1, 2012 to August 20, 2012.