Third Level Assessment– Aquatic and Riparian Habitat

iBoF Atlantic salmon

The modern decline in iBoF salmon within the Petitcodiac is a marked contrast to the abundance described by early settlers. This, despite Gubbin’s 1811 report that salmon were introduced to the Pollett by English settlers shortly after their arrival (Gubbins 1980). As discussed in more detail in the First Level Assessment Agricultural Practices, that report makes little sense, and while settlers may have believed that they had done so, it is most likely a misinterpretation of events. Construction of the Moncton to Riverview causeway in 1968 eliminated fish passage for adult salmon and smolts and effectively (but for ongoing intervention) extirpated the species from a river system that represented 20% of the total iBoF population (Locke et al. 2003). That said numbers of this species had been decreasing for decades due to the impacts of other human activities (Elson 1962), long prior to construction of the causeway.

Locations where iBoF Atlantic Salmon have been observed are shown in Figure 7. Survival and development of fry released along the Pollett since the causeway gates were opened in 2010 have been monitored by annual electrofishing at the release sites, and near the mouth of the river through operation of a Rotary Screw Trap (RST) or “smolt wheel” a counting fence, and fyke nets. Release sites included locations upstream of Gordon Falls, where quality habitat exists, even though there is some question if salmon would be unable to access it naturally. The decision was made to use that portion of the river as well since such areas could provide nursery habitat for juveniles (who then migrate out as smolts), despite them possibly being unable to return that far upstream as adults.

Figure 7: iBoF Atlantic salmon occurrences within the Pollett River

In recent years, adult salmon have been released into the river- both non-targeted fish from DFO’s Live Gene Bank at Mactaquac with the addition during the last several years of Fundy Salmon Recovery (FSR) adults grown to maturity in sea cages in Grand Manan. These FSR adults are of particular significance as they are wild exposed fish from the Petitcodiac River itself (Fundy Salmon recovery 2023). This means that unlike the DFO fish, which though wild exposed were collected as juveniles from the Big Salmon River (BSR), adult salmon released into the Petitcodiac as part of the FSR program were typically collected as juveniles (smolts of fall parr) within the Petitcodiac. These individuals would be either the offspring of DFO adults released into the Petitcodiac during previous years, or unfed fry from DFO’s Live Gene Bank. Having lived their early life stages within the Petitcodiac, juveniles collected there and sent to the FSR sea cages have 1) undergone natural selection for conditions in the Petitcodiac, and 2) recognize it as their natal stream, preferentially returning to it to spawn (rather than the BSR).

Data collected during this process bares this out. Most FSR adults are collected as juveniles on the Pollett River, with a small subset coming from next door on the Little River. In the late summer and fall of 2021 four PIT tagged salmon were detected returning to the Little River by an automated PIT tag reader antenna array FFHR operates located at the 895 bridge. Of these salmon three were FSR Little River origin fish, having been collected near that bridge in 2019 as smolts, raised to adulthood in Grand Manan and released on the Pollett River (where all FSR fish are released) in the fall of 2020. Yet in 2021, when these Little River salmon returned on their own to spawn yet again, they did so preferentially to their natal river. Subsequently, in 2022 electrofishing detected fry in that part of the Little River (where no fry or adults had been released) indicating that successful spawning took place nearby in 2021.

Completion of the new bridge between Moncton and Riverview in 2021 to partially replace the Petitcodiac Causeway has strongly advanced iBoF Atlantic salmon recovery efforts in the Petitcodiac. That fall, the first wild returning adult was captured downstream of the Pollett at the head-of-tide in Salisbury on October 4th. She lacked both a PIT tag and a floy tag. She showed no scars from having shed either type of tag, nor did it look as though a tissue sample had been taken from her caudal fin. In short, there was no sign that she had been previously handled- so scale and tissue samples were taken to allow further investigation. Stable Isotope Analysis carried out by the Stable Isotopes in Nature Laboratory (SINLAB) at the University of New Brunswick (UNB) confirmed that she was a returning wild iBoF Atlantic salmon (Samways personal communication 2021), never handled by FFHR prior to her capture.

Examination of the scale sample indicated that she was a 2-sea-winter (2SW) fish, who had smoltified and gone to sea in 2019 as a two-year old smolt. As such, she would have been at sea in both December 2020 and December 2019. Having been captured on the main stem of the Petitcodiac beyond the mouth of the Little River, it seems reasonable to speculate that she was on her way upstream back to the Pollett River. Based on that, it is likely that she exited the Pollett as part of the Spring 2019 smolt run. FFHR’s 2019 data indicates a Bayesian Pollett smolt run size estimate of approximately 5,465 smolt. The tissue sample is still available and could be used for genetic analysis. Doing so may shed light on what part of the program she resulted from. One way or another, most smolt coming off the Pollett are present due to FFHR’s stocking efforts. Being a two-year old smolt in 2019, she was probably either the offspring of the 126 Fundy Salmon Recovery adults released in October 2016 or one of 47,000 fry (directly sourced from the DFO Live Gene Bank at Mactaquac) released in May 2017. The adults in 2016 were split evenly by gender: 63 males and 63 females. In the upper Pollett 64 were released (35 male 29 female) and 62 were released in the lower Pollett (28 male and 34 female). All the redds found in 2016 were in the lower half of the Pollett- a typical result based on Figure 7. Fry released in 2017 were put into Webster Brook, in the upper Pollett near Elgin. Having come directly from Mactaquac there ought to be good records of the ancestry of the fry. If she wasn’t released as a fry in Spring 2017 then one if not both of her parents were probably among the adults released in the Fall 2016.

She is probably not alone – the FNT merely samples what is in the river. Catching one indicates that numbers have reached a level where the trap can detect them. It is premature to attribute detection of the wild salmon in 2021 entirely to the new channel under the bridge. That said however, she must have passed under the bridge, and the improved passage can only have helped her to return. No additional returning wild adults were caught during the following year. The lack of such fish in 2022 was noteworthy, and though somewhat disappointing, not particularly surprising. It does not mean that the individual caught in 2021 was a fluke, but merely highlights the fact that catching the first wild return was an unusual event. Two things can be simultaneously true: i.e. that the odds of catching such a fish have increased as a result of ongoing iBoF Atlantic salmon recovery efforts, and that yet such fish are still uncommon enough that doing so remains unlikely.