The following is a summary of the focus areas in which research scientists will conduct their work. These trials will be conducted onboard chartered fishing vessels and during regular fishing trips.
1. Passive mitigation of bycatch
a. Instrumented buoys (echosounder, etc.)
The idea is to use instrumented buoys to have remote information on the presence/abundance of by-catch versus catch species. The protocol will concern the groundtruthing of data collected by echosounder buoys attached to FADs through (i) the concurrent collection of depth data of various species at the FAD (tunas, sharks, oceanic triggerfish, rainbow runner, etc.) equipped with pressure sensitive acoustic tags and (ii) the catch of the entire aggregation by a PS.
b. Ecological FADs : (i) turtle -and shark-friendly, (ii) biodegradable FADs
Ecological FADs will be deployed during the project in order to test their life time (in case of biodegradable materials) and their efficiency in attracting tunas without entangling turtles and sharks.
c. Effect of design of FADs on the composition of fish aggregations
First analysis using observer data will be done. Upon results of this analysis, some tests can be performed at sea.
2. Avoid catching bycatch before setting
a. Pre-estimation of by-catch
Two parallel approaches were discussed during the meeting :
1) Groundtruthing the information from the PS’ echosounder/sonar by using camera/ROV prior to setting, in order to help fishers better estimate by-catch
2) Improving the use of some echosounders (e.g. SIMRAD ES60) by joint collaboration between skippers and scientific acousticians
Both approaches require that the entire aggregation be captured to validate the estimation.
b. Natural behavior of fish at FADs
The objective is to observe whether or not tunas and sharks regularly leave the immediate vicinity of the FAD during a 24-h cycle. This information could be used to target schools with less bycatch (see point 2c). Some of these FADs could be abandoned for long term observations of behavior (which will also allow the study of the ecological trap hypothesis), while others could be fished.
c. Skippers’ ability to catch free-swimming schools of skipjack (SKJ) away from FADs
Results from the study of the natural behavior of tunas around FADs (see point 2b) will provide a basis for determining the best time of day to target free-swimming schools of SKJ after they leave the FAD.
The PS’ skipper will be asked to catch schools of SKJ that were observed leaving the immediate vicinity of the FAD while the schools of BET are expected to remain closely associated with the FAD. The idea is to test whether it is possible to use FADs as “providers” of free-swimming schools of SKJ where by-catch is known to be lower. We know that such a strategy could induce more null sets than setting around the FAD but the benefits in by-catch reduction could be significant. Preliminary analysis of observer data seems to suggest that some skippers may have successfully adopted this strategy during the FAD closure in the WCPO this year.
It will be important to validate that the school of SKJ came from the FAD. This could be done through two different approaches:
1) During experiment 2b, acoustically tagged SKJ will be actively tracked (Vemco VR28) and the school will be tracked by the PS’ sonar
2) Other experiments could consist of conventional tagging of SKJ while they are at the FAD and examine if the captured school contains tagged SKJ.
d. Double FADs
This has been recognized by the committee as the most novel idea to be tested with the most unpredictable outcome. The principle is to assess whether any segregation occurs when a single aggregation is exposed to two competing aggregating devices (which has been shown for some terrestrial species). Single FADs with two identical components will be deployed. After some time, they will be visited and split to observe if any species segregation occurs. Failing this, modifications of one of the two components of the single FAD will be tested (e.g. a deep versus a shallow component, see Nelson’s double FAD) to find stimuli that could enhance species segregations.
e. Attraction of sharks away from FADs
The idea is to test different stimuli (chum) to attract sharks away from the FAD shortly before the net is set.
3. Release from the net
a. Behavior of fish in the net
This activity will provide baseline data for activities 3b and 3c. The skipper will be asked to keep the net open for some time during daylight hours in order to observe the behavior of fish. The behavior will be observed through various techniques including acoustic tagging, sonars, videos (ROV), visual observations from the PS (crow’s nest).
b. Behavioral manipulations (e.g. attraction of sharks, small BET, other finfish)
The idea is to test different stimuli (chum) to attract sharks out of the net (when towing the FAD away), or others (e.g. light) to attract fish (e.g. small BET or other finsfish) towards an area in the net.
c. Modifying the selectivity of the gear (e.g. sorting grids, changing mesh size, etc.)
Jacques Sacchi will make a review of different options (including sorting grids of different designs, sections of the seine with large square meshes, etc.) and will propose a list of priorities to be tested during the project. As this activity will not be done during the first cruise, the protocols to be tested will be discussed at the second meeting of the committee, along with inputs from 3a that will be done during the first cruise.
4. Release from the deck
a. Best practices for handling sharks onboard
For small sharks, the best practices will involve recommendations for manual handling. For larger sharks, some handling equipment will be developed and tested (e.g. the ones proposed within the MADE project).
b. Survival of released sharks
Initially, only the liveliest sharks will be tagged (with pop-up archial tags – PATs) and released as soon as possible to study their survival. The idea is to use MiniPATs from Wildlife Computers (WC) as most of sharks will be small.
Blood samples will be taken to establish baseline data on stress levels at the time of release.
