174 
Fishery Bulletin 1 14(2) 
Table 3 
Absolute error (in metric tons, t), for biomass estimates (t) and real catch (t), from 
each of the two methods analyzed in this study for 21 sets conducted by a commercial 
Spanish purse seiner in the Atlantic Ocean between 2009 and 2011. Shown also are 
the biomass estimates originally provided by the Satlink buoy (S) with the use of an 
algorithm based on skipjack ( Katsuwonus pelamis) and the final biomass estimates 
obtained with the new method (NM) proposed in this study. 
Buoy code 
Catch 
(t) 
Biomass 
estimate 
(t) (S) 
Absolute 
error 
(t) (S) 
Biomass 
estimate 
(t) (NM) 
Absolute 
error 
(t) (NM) 
23753 
20 
12 
-8 
17.66 
-2.34 
23728 
24 
8 
-16 
25.84 
1.84 
23737 
10 
20 
10 
21.90 
11.90 
23825 
150 
81 
-69 
141.58 
-8.42 
23737 
20 
121 
101 
44.88 
24.88 
23825 
14 
10 
-4 
16.60 
2.60 
23751 
60 
38 
-22 
32.43 
-27.57 
23750 
50 
84 
34 
68.60 
18.60 
28171 
18 
16 
-2 
19.23 
1.23 
23736 
35 
31 
-4 
28.21 
-6.79 
28179 
25 
11 
-14 
17.13 
-7.87 
28184 
80 
63 
-17 
49.88 
-30.12 
28643 
42 
106 
64 
36.09 
-5.91 
28471 
30 
17 
-13 
17.13 
-12.87 
28707 
15 
14 
-1 
18.71 
3.71 
28697 
12 
32 
20 
28.81 
16.81 
30528 
7 
2 
-5 
14.48 
7.48 
28390 
20 
11 
-9 
16.07 
-3.93 
28216 
15 
14 
-1 
18.71 
3.71 
28705 
30 
59 
29 
44.88 
14.88 
30530 
20 
16 
-4 
18.18 
-1.82 
tuna species biomass per set was estimated at 0.627 
t (min=0; max=12.398; SD=2.37), which fitted reason- 
ably well with the values found in the Atlantic Ocean 
for the European purse seine fleet (mean=0.79; min=0; 
max=22.06) (Amande 13 ). 
Discussion 
Echosounder buoys are widely employed by the indus- 
trial tropical tuna purse seine fishery and their use 
has rapidly increased since their introduction into the 
market in the mid-to-late 2000s (Lopez et al., 2014). 
In fact, Baske et al. 1 estimated an annual production 
of 50,000-70,000 satellite-tracked buoys by the major 
buoy-producing companies, of which most were fitted 
with echosounders. However, this source of informa- 
tion needs to be evaluated and validated before use in 
fisheries applications. We present a processing method 
that takes into account the multispecies and multisize 
nature of DFAD-associated aggregations. The method 
13 Amande, M. J. 2012. Personal commun. Centre de Re- 
cherces Oceanologiques, CRO, 29, Rues des pecheurs, BP V 
18, Abidjan, Cote d’Ivoire. 
substantially improves the overall precision of the orig- 
inal biomass estimation (error variability and the rang- 
es of underestimation and overestimation have been 
notably diminished) and also provides biomass data by 
major species groups, rather than a single information 
unit on the entire fish aggregation based only on one 
species of tuna (i.e., skipjack tuna). 
Echosounder buoys for scientific studies 
The method developed in the present study shows the 
potential for echosounder buoys as small autonomous 
tools that can provide information on fish aggregations 
at DFADs over weeks and months. Echosounder buoys 
attached to FADs could constitute ideal observational 
platforms, providing data on the fish community associ- 
ated with floating objects. Monitoring of FAD buoy data 
could then provide a powerful tool for scientific evalua- 
tion of resource abundance and for improved knowledge 
of the associative behavior of the fish communities as- 
sociated with FADs. In order to increase the sampling 
potential and data input, scientists should consider 
similar studies on the other echosounder buoy brands 
currently used by industrial purse-seine operators and 
which are not addressed in the present study. 
