harbour_seals: Estimated abundance of Pacific Harbour Seals in each of seven...

In pbs-assess/PACea: An R package of Pacific ecosystem information to help facilitate an ecosystem approach to fisheries management

Estimated abundance of Pacific Harbour Seals in each of seven regions

Description

The Pacific Harbour Seal (Phoca vitulina richardsi) is the most abundant pinniped species in the Northeast Pacific and is found throughout coastal and estuarine waters of British Columbia. A coastwide survey of harbour seals was conducted from 2015 to 2019 and used to inform the estimated trends in abundance given here.

Usage

harbour_seals

Format

A tibble also of class 'pacea_harbour_seals' with columns:

date:

Date of the GAM estimate of abundance; there is a time step of about 250 days in the GAM, hence some years have more than one value and so we give a date rather than a year

region:

the region that the estimate corresponds to; one of SOG, WCVI, QCS, DP, CMC, NMC, HG, or Coastwide

low:

low end of the estimate of abundance, defined as the upper value of the 95 scale) from the GAM

mean:

mean estimate of abundance, numbers of seals (in that region)

high:

high end of the estimate of abundance, defined as the lower value of the 95 scale) from the GAM

Details

The Pacific Harbour Seal stock in Canada is assessed as a single stock. The coastwide abundance of harbour seals in British Columbia was assessed through aerial surveys conducted over multiple years, and corrected for area covered, survey timing relative to peak pupping, and proportion of seals hauled out during surveys. Estimated abundance was calculated for seven regions: the Strait of Georgia (SOG), West Coast Vancouver Island (WCVI), Queen Charlotte Strait (QCS), Discovery Passage (DP), Central Mainland Coast (CMC), Northern Mainland Coast (NMC), and Haida Gwaii (HG); see Figure 1 of DFO (2022) for a map showing the regions. The coastwide estimates are also given (labelled 'Coastwide' so the plot title is capitalised), for which the means are calculated as the sum of the regions' means and the 'low' and 'high' values as TODO ???

The estimated abundances were calculated using Generalised Additive Models (GAMs), and are included here (reproducing the trends shown in Figure 3 of DFO, 2022). See that figure to see the amount of data available in each region; these data can be added to 'pacea' if desired – please let us know. The final year of data in each region is saved in the object 'harbour_seals_data_final_year'.

For further details see DFO (2022), from which some of the above text was adapted. Full details of the underlying modelling should be available in the resulting Research Document (check https://www.isdm-gdsi.gc.ca/csas-sccs/applications/events-evenements/result-eng.asp?DateMatch=on&StartDate=&ToDate=&mode=0&desc=PHOCA+VITULINA+RICHARDSI&mode1=0&location=&B1=Search for updates).

DFO. 2022. Stock Assessment of Pacific Harbour Seals (Phoca vitulina richardsi) in Canada in 2019. DFO Canadian Science Advisory Secretariat Science Advisory Report. 2022/034. https://www.dfo-mpo.gc.ca/csas-sccs/Publications/SAR-AS/2022/2022_034-eng.html

See also: 'harbour_seals_data_final_year' for the year of the final data for each region.

Author(s)

Andrew Edwards

Source

Estimates provided by Strahan Tucker, then wrangled and imported using 'data-raw/mammals/harbour-seals/harbour-seals.R'.

Examples

## Not run: 
harbour_seals
plot(harbour_seals)
plot(harbour_seals, region = "SOG")
plot(harbour_seals, include_coastwide = FALSE)

## End(Not run)

pbs-assess/PACea documentation built on April 17, 2025, 11:36 p.m.