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Factors Affecting Poor Salmon Survival in Northeastern PEI

Successful Applicant: University of Prince Edward Island



Project Title: Factors Affecting Poor Salmon Survival in Northeastern PEI

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Project Summary:

Despite extensive Atlantic Salmon habitat restoration poor recruitment has been reported in PEI streams were substantial numbers of redds are observed. One of these streams is Priest Pond Creek PEI where this ongoing two-year study sought to examine the reasons for poor recruitment. The hypotheses are that eggs are not hatching/fry not emerging, or fry are not making the transition of exogenous feeding primarily due to temperature. The goal of this research is to be benefit wildlife by contributing to Atlantic Salmon management practices on PEI over the long-term with the ultimate goal to restore wild salmon populations.

Rivers where project took places were West River, North Lake Creek, Priest Pond Creek, PEI. Three-pass electrofishing surveys conducted in six 50 m reaches adjacent to known spawning redds throughout the system in fall 2019 confirmed that there was recruitment failure in Priest Pond Creek as compared to the other two rivers. All three rivers had substantial numbers of identified salon redds over the past few years. Mean juvenile salmon density was 14.4, 10.6, and 0 individuals per 100 m² in West River, North Lake Creek, and Priest Pond Creek, respectively. The only individuals captures in Priest Pond Creek were three parr. Thus, little or no recruitment could be observed for the third year out of the last four, confirming the basis of the present study hypotheses.

Temperature monitoring was conducted in all streams from May 2019 and is still ongoing. At least five loggers were placed in the streams from the headwaters to the head of tide. As PEI streams are very short and fed with groundwater along their length, the increase in temperature moving downstream was less than 3°C. The exception only occurred in Priest Pond Creek just below Harmony Junction Pond. From the perspective of the hypothesis that temperature may be impacting the switch to exogenous feeding, temperatures in June and July are most critical. June mean temperature ranged from 9.1-11.5°C, 7.9-11.4°C and 10.7-15.1°C while July mean temperature ranged from 10.4-13.0°C, 7.7-12.0°C, and 11.6-19.1°C in West River, North Lake Creek, and Priest Pond Creek, respectively. Based on these early data, the hypothesis that water in Priest Pond Creek is too cold to allow the switch to exogenous feeding seems very unlikely. North Lake Creek is typically colder than the other streams, and has excellent recruitment. Priest Pond Creek is typically warmer than the other systems due to a pond located in the headwater. Regardless, any very minor temperature differences are unlikely to explain a complete recruitment failure throughout the stream.

Redd surveys have been underway since November. While numerous redds were observed in West River, the remaining two sites appear to spawn much later than this site (potentially consistent with a different genetic strain in this area as has previously been determined). Redds are currently being identified for confirmation and instrumentation in early January. The pilot study conducted to determine methods to measure oxygen within redds was successful and redd oxygen data loggers will be installed shortly.

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