Sustainable livelihoods in Torres Strait

The importance of sea cucumber fishing

Nicole Murphy

Oceans and Atmosphere

Introduction

Most of my work is in Torres Strait in collaboration with Traditional Owners, with a focus on stock assessment and harvest strategies for their hand collectable fisheries. I have spent a lot of time underwater collecting data and I now spend a lot of time with data outputs and analyses. I never used code before data school.

My Project

The Torres Strait ‘Beche-de-mer’ (sea cucumber) Fishery (TSBDM) has become an important source of income for Torres Strait islanders since the early 1990s. While most beche-de-mer stocks are in good numbers, several species are closed to fishing, or recovering from fishing pressure. This has led to increased fishing pressure on other species in the fishery. A stock survey is at present, the only way to find out the status of fished sea cucumber populations in Torres Strait. Previous stock surveys have been undertaken in 1995, 2002, 2005 and 2009, with the most recent surveys undertaken in Novemeber 2019 and January 2020.

Thank you to Torres Strait fishery representatives and Traditional Owners, for regularly hosting us on their land and supporting this research.

My goals

Previously Excel has been used for anlayses for stratitfied mean comparisons and stock estimates of sea cucumber abundance. My initial goal was to work up the 2019/20 data set and combine with previous survey data, to produce some length frequency plots, which I did - nice one! I then moved onto looking at average density estimates, over survey years for sea cucumber species.

Stock survey

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SCUBA divers surveyed reef top, reef top buffer and reef edge transects for sea cucumbers species. Sea cucumbers were processed and data recorded, along with a number of environmental indicators and habitat measurements (Table1).


Table 1: Field data
holothuria_whitmaei zone samocc strata count_site_id area_hectare longitude latitude depth_finish
6.4523810 Barrier 2002 Reef edge 25 4263.384 144.0456 -10.186410 17.7600000
0.0000000 Barrier 2002 Reef top 2 2599.626 143.9492 -10.411155 2.5000000
8.9285714 Barrier 2002 Reef top buffer (200 m) 14 9341.058 143.9927 -10.300327 0.0000000
0.2604167 Cumberland 2002 Reef edge 48 4679.308 143.7410 -9.996976 17.5729167
2.3148148 Cumberland 2002 Reef top 54 30938.752 143.6748 -10.032286 0.3148148

Selfie with a White teatfish, Holothuria fuscogilva

Plots from R

Initial data anlayses for some of the high and medium value commercial sea cucumber species looked at length frequency profiles (Figure1), as well as average density estimates across survey years (Figure2).

Length frequency distribution for Black teatfish _Holothuria whitmaei_, over survey years.Length frequency distribution for Black teatfish _Holothuria whitmaei_, over survey years.

Figure 1: Length frequency distribution for Black teatfish Holothuria whitmaei, over survey years.


When less is definitely more, but it was cool to see what outputs can be produced.
A = White teatfish, _Holothuria fuscogilva_ B = Black teatfish, _H. whitmaei_ C = Curryfish, _Stichopus herrmanni_ D = Prickly redfish, _Thelenota ananas_

Figure 2: A = White teatfish, Holothuria fuscogilva B = Black teatfish, H. whitmaei C = Curryfish, Stichopus herrmanni D = Prickly redfish, Thelenota ananas

Favourite tools

        

My time went …

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   It was a rollercoaster! I appreciate the fact that you can type anything into google and guaranteed someone has already aksed
   the question and there are answers, especially stack overflow. The R community are rockstars.



Next steps

I plan to use ggplot to plot current Catch Per Unit Effort data for the TSBDM fishery and will look at writing functions to capture other analyses currently run in Excel. I will also be trying out modelr (and other options) for looking at modelling stock trends for sea cucumber species.

My Data School Experience

In addition to building on outputs from data school for my current sea cucumber project, I have already used R for real on other project work. A figure for a report needed updating with recent data, however the scientist that produced the plot has retired. I was able to write the script and generate the exact plot, this has now been included in the technical report for the project milestone.

One day it just clicks and it’s kind of awesome.
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Acknowlegement: Thanks to Stephen Pearce, Kerensa McElroy and Kristian Goodacre, as well as all the guest teachers and tutors, also rockstars!