Science Advisory Report 2009/029
Evaluation of Atlantic Sturgeon (Acipenser oxyrinchus) in the Maritimes Region with respect to making a CITES Non-Detriment finding
- The abundance of Atlantic sturgeon in the Saint John River has never been formally assessed, and the current population size is unknown.
- Age structure of Atlantic sturgeon in the Saint John River is unknown. Length data collected from the commercial harvest in 1998/1999 and 2007/2008 indicates a similar size structure in these two time periods. Application of the size at age curves from the St. Lawrence River population indicates that the age distribution of spawners in the exploitable population in the Saint John River is likely broad with at least 20 age classes represented.
- More females were captured in 2007/2008 than in 1998/1999, which suggests mature females currently comprise a larger component of the exploitable population.
- Current recruitment of Atlantic sturgeon is unknown but is suspected based on the ongoing presence of juvenile fish in the Saint John River and the broad size structure of the exploitable population. Preliminary data also suggests that there may be an abundance of juveniles in the Minas Basin, although it is not clear if these fish are residents in the Bay of Fundy.
- The primary source of human-induced mortality of Atlantic sturgeon in the Saint John River is from the commercial fishery. The recreational fishery has a release rate of approximately 98%, and survival of sturgeon released live is considered to be very high. Some sturgeon are authorized by DFO to be caught and retained for aquaculture purposes (i.e., for breeding). It is prohibited to retain Atlantic sturgeon captured as bycatch in other fisheries. The Annapolis Tidal Generating Station is known to be a source of mortality for Atlantic sturgeon in the Bay of Fundy; however, the number of individuals reported to be killed each year is low (<5) and the proportion of these that are from the Saint John River is not known.
- The total number of Atlantic sturgeon removed (all sources) from the Bay of Fundy population each year has not been accurately quantified. However, the number of fish removed by the commercial fishery (only in the Saint John River) is estimated to be approximately 400 individuals per year since 1965. In 2005, the recreational fishery removed a possible 41 Atlantic sturgeon.
- At present, DFO does not possess sufficient information to allow for accurate estimation of the potential harvestable surplus of Atlantic sturgeon from the Bay of Fundy, nor specifically from the Saint John River. However, there is no evidence that the average annual reported landings from 1965-2002 of 12.6 mt, or approximately 400 fish, has resulted in any significant changes to the observed relative abundance or age structure of Atlantic sturgeon in the Saint John River.
- The exploitable population of Atlantic sturgeon in the Saint John River appears to have a healthy age structure and has supported an average annual commercial harvest in the order of 400 fish per year over the past 40 years. Other sources of human-induced mortality on Atlantic sturgeon in the Bay of Fundy are thought to be low and in the order of approximately 50 fish per year. Non-fishery sources of human-induced mortality are not expected to change from present levels during the next 5 years.
- A maximum commercial harvest of 350 Atlantic sturgeon from the Saint John River is considered to be sustainable over the short-term (5 years). The sex ratio of this harvest should also be taken into consideration, with a suggested male to female ratio close to 50:50.
- A formal species assessment including the acquisition of robust life history, abundance, and age-structured genetic data is recommended before future harvests are considered.
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