CCAMLR

We wish to draw the attention of Members to an online application of the R code published in the attached paper. The web-based app ‘photoR’ (https://jefferson.shinyapps.io/photor2) implements  the methods of the paper and provides summary outputs for direct input to CEMP A6b and A9 eforms. The abstract of the paper follows:

Summary

1. Collecting spatially extensive data on phenology and reproductive success is important for seabird conservation and management, but can be logistically challenging in remote regions. Autonomous time-lapse camera systems offer an opportunity to provide such coverage.

2. We describe a method to estimate nest-level breeding phenology and reproductive success of colonial Pygoscelid penguins using photographs from time-lapse cameras. The method derives from stereotypical patterns of nest attendance, where predominantly two adults are present before and during egg laying, but switch to one adult during incubation. The switch approximates the date of clutch completion and is estimated by fitting a smoothing spline to daily nest attendance data, identifying candidate dates that switch from two adults to one, and selecting the date when the first derivative of the spline is minimized. Clutch initiation and hatch dates are then estimated from the mean, species-specific interval between egg laying (Pygoscelid penguins typically lay two eggs) and the duration of the incubation period. We estimated these intervals for each species from historical field data. The phenology is adjusted when photographs indicate egg or chick presence prior to their estimated lay or hatch dates. The number of chicks alive in each study nest on its crèche date determines reproductive success estimates. The method was validated with concurrent direct observations for each species and then applied to a camera network in the Antarctic Peninsula region to demonstrate its utility.

3. Mean egg lay and incubation intervals from direct observations were similar within species across sites. In the validation study, the mean clutch initiation, hatch, and crèche dates were generally equivalent between photographs and direct observations. Estimates of reproductive success were identical. Applying the method to a time-lapse network suggested relatively high reproductive success for all species across the region and corroborated general understanding of latitudinal trends and species-level plasticity in phenology.

4. The method accurately estimated phenology and reproductive success relative to direct observations and appears well-suited to operationalize regional time-lapse camera networks. The estimation method should be applicable for other seabirds with stereotypical nest attendance patterns from which breeding phenology could be estimated.

Sea ice is a major constraint of fishery performance in the Southern Ocean seasonal sea ice zone. We use sea ice concentration data from 2002-2017 that cover the wider Weddell Sea to establish statistical models of (i) accessibility, i.e. the probability that a particular area is navigable by fishery vessels at a given time, and of (ii) repeated accessibility, i.e. the probability that a particular area is navigable by fishery vessels at a given time and again within the following two years, as requested by CCAMLR research fishery regulations. Our findings indicate that under the actual sea ice conditions almost 50% of the entire WSMPA Planning Area is not suitable for fishery vessels at any time of the year, while there are high spatiotemporal variability in repeated accessibility in particular areas such as along the ice shelf of the eastern and south-eastern Weddell Sea. We consider our models to constitute valuable, riskreducing planning tools in the further development of fishery research as well as of ship-bound tourism in the wider Weddell Sea area.

The one nautical mile integrated Nautical Area Scattering Coefficient (NASC) values of four surveys in 48.1 fishing area were calculated using both the swarm-based and conventional grid-based acoustic data processing methods. All parameter settings were consistent with the reports of SG-ASAM-2017 except that the dB difference window of Sv_{120 kHz}-Sv_38kHz is set 0 to 20 dB. And the two groups of results were compared by correlation, linear regression analysis and nonparametric significant difference tests (Kruskal-Wallis tests) to examine the validation of the developed swarm-based method for Antarctic krill density estimation. The comparisons suggest that the calculated NASC values of swarm-based and grid-based method show non-significant difference and significant linear relationship for all the four surveys. Therefore, it is concluded that the krill density estimated by swarm-based and grid-based method could be of good agreement.

During the meeting, the subgroup suggested further analysis on swam-based approach and grid-based approach based on data in the paper. In accordance to the suggestions, further analyses were undertaken and the results were shown in Appendix A.

The distribution and abundance of krill aggregation inhabiting the Subarea 48.1, which includes the Elephant Island peripheries and the west and south of the South Shetland Island, were estimated using an acoustics survey. Acoustic data were collected with 38 and 120 kHz from April 13 to 24 in 2016 and 38 and 200 kHz from March 6 to 14 and 38 and 120 kHz on April 27 and May 5 in 2017. Krill were collected by the commercial middle trawl fishing vessel. The data were processed and analyzed following CCAMLR standard protocols using swarm integration (SHAPES module within that software for swarm identification) based on data from a transect-based survey. The weighted krill density and biomass were estimated to be 0.20 g/m² and 18 thousand tons (CV=33.8%) applying S_v difference 3.96-5.91 dB and 0.92 g/m² and 83 thousand tonnes (CV=31.4%) applying S_v difference -3.0-13.8 dB in 2017, respectively. Krill density and biomass were significantly higher in 2016 than those in 2017.

Hydroacoustic data were collected to study the distribution and abundance of Antarctic krill relative to their predators in the Southern Ocean during annual logistic summer trips and dedicated research winter trips to Antarctica on board the South African RV SA Agulhas II. The 38, 120 and 200 kHz transducers mounted on the drop keel of the research vessel were used to collect acoustic data; where the first year (2014) of the study logged acoustic data during daytime only whilst surveys in later years (2015-2016) logged data all day long. Target sampling was conducted using the Methot ichthyoplankton net, zooplankton nets and buckets. Preliminary results from those surveys are summarised herein. Collections of acoustic data from dedicated and opportunistic surveys for this work indicate that the RV SA Agulhas II can be effectively utilised for acoustic research. Furthermore, this vessel provides allowance for other essential concurrent research including oceanographic sampling and top predator observations.