166 
NOAA 
National Marine 
Fisheries Service 
Fishery Bulletin 
established 1881 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
A model based on data from echosounder 
buoys to estimate biomass of fish species 
associated with fish aggregating devices 
1 AZTI-Tecnalia 
Herrera kaia 
portualdea z/g 
20110 Pasaia (Gipuzkoa), Spain 
2 Institut de Recherche pour le Developpement 
IRD, UMR EME 212 
Avenue Jean Monnet 
CS 30171 
34203 Sete Cedex, France 
3 International Seafood Sustainability Foundation (ISSF) 
805 15th Street NW 
Washington, D.C. 20005 
Abstract— Most of the drifting fish 
aggregating devices (DFADs) used 
in industrial tropical tuna purse- 
seine fisheries are equipped with 
satellite linked echosounder buoys, 
which provide fishing crews with 
remote, accurate geolocation infor- 
mation and rough estimates of FAD- 
associated tuna biomass. One of the 
most common brands of echosounder 
buoys (SATLINK, Madrid, Spain) is 
currently calibrated for the target 
strength of skipjack tuna ( Katsu - 
wonus pelamis ) and provides bio- 
mass data on that species. Using that 
brand of echosounder buoy, we devel- 
oped a new behavior-based approach 
to provide relative biomass estimates 
and a remote target classification of 
fish aggregations at FADs. The model 
is based on current knowledge of the 
vertical distribution of the main fish 
species associated with FADs, as well 
as on appropriate TS and weight val- 
ues for different species and sizes, 
and is further based on parameter 
optimization against a set of fishing 
operations on DFADs. This model 
reduced the error variability in bio- 
mass estimates by about 60% and 
also reduced the ranges of underes- 
timation and overestimation by 55% 
and 75%, respectively. Similarly, the 
original coefficients of correlation 
and determination were also consid- 
erably improved from 0.50 and 0.25 
to 0.90 and 0.82, respectively. We dis- 
cuss how this new method opens new 
opportunities for scientific studies 
and has implications for sustainable 
fishing. 
Manuscript submitted 14 August 2015. 
Manuscript accepted 29 January 2016. 
Fish. Bull. 114:166-178 (2016). 
Online publication date: 23 February 2016. 
doi: 10.7755/FB.l 14.2.4 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Jon Lopez 1 
Gala Moreno 1 - 3 
Guillermo Boyra 1 
Laurent Dagorn 2 
Email address for contact author: jlopez@azti.es 
Objects floating on the surface of 
the tropical and subtropical oceans 
attract a number of marine species, 
including tropical tunas (Castro et 
al., 2002; Taquet et al., 2007b). Tak- 
ing advantage of this associative 
behavior, tropical tuna purse sein- 
ers regularly deploy drifting, man- 
made floating objects, also called 
drifting fish aggregating devices 
(DFADs), to facilitate their catch of 
skipjack ( Katsuwonus pelamis), yel- 
lowfin ( Thunnus albacares) and big- 
eye ( Thunnus obesus) tunas. This 
fishing method is essential for the 
current operation of purse-seine 
fleets in all oceans; more than 50% 
of purse-seine sets (and greater than 
70% of purse-seine sets during some 
years in the Indian and eastern 
Pacific Oceans) are made on float- 
ing objects. This method accounts 
for nearly half of the world’s tropi- 
cal tuna catch (Dagorn et al., 2013). 
Indeed, it has been estimated that 
50,000-100,000 DFADs are deployed 
annually worldwide (Baske et al. 1 ; 
Scott and Lopez 2 ), which drift at sea 
on average for periods of over one or 
two months depending on the ocean 
(Maufroy et al., 2015). However, the 
increasing use of DFADs has led to 
concerns. Setting on floating objects 
contributes to the catch of small 
and undesirable sizes of bigeye and 
yellowfin tuna that are usually not 
caught by sets on free-swimming 
1 Baske, A., J. Gibbon, J. Benn, and A. 
Nickson. 2012. Estimating the use of 
drifting fish aggregation devices (FADs) 
around the globe, 8 p. PEW Environ- 
mental Group, 901 E Street NW, Wash- 
ington, D.C. 20004. [Available at web- 
site.] 
2 Scott, G. P., and J. Lopez. 2014. The 
use of FADs in tuna fisheries. Europe- 
an Union, European Parliament, Policy 
Department B: Structural and Cohesion 
Policies, Fisheries IP/B/PECH/IC/2013- 
123, 70 p. [Available at website.] 
