A Snapshot of the Tropical Tuna Purse Seine Large-Scale Fishing ...

ISSF Technical Report 2012-01
A Snapshot of the Tropical Tuna Purse Seine Large-Scale Fishing Fleets
At the End of 2011
Victor R. Restrepo * and Francesca Forrestal **
January 10, 2012
* Chair, ISSF Scientific Advisory Committee, Vrestrepo@iss-foundation.org
** University of Miami, Rosenstiel School of Marine and Atmospheric Science, Fforrestal@rsmas.miami.edu
1. Introduction
Purse seine fishing vessels catch nearly 65% of the 4.4 million tonnes of tunas taken
annually worldwide (ISSF, 2011). Of the tropical tunas, purse seiners generally target
skipjack and yellowfin, though they also catch bigeye tuna associated primarily with
floating objects.
In recent years, several authors have estimated the number of vessels and fishing
capacity of tropical tuna purse seine fleets either regionally (e.g., Gillett and Lewis,
2003) or globally (Joseph, 2003; Reid et al., 2005). One of the aims of this paper is to
provide a "snapshot" of the purse seine fleet as of the end of 2011 for comparative
purposes.
In addition, there is a growing interest by decision-makers regarding the need to
manage the fishing capacity of the purse seine fleet. For instance, at the Third Joint
Meeting of Tuna RFMOs (La Jolla, California, USA, July 2001), participants recommended
"...that developed fishing members freeze large scale purse seine capacity under their flag",
while developing a scheme for how to reduce fishing capacity and transferring capacity
to coastal states that have a right to increased participation in the fisheries (TRFMO,
2011).
While this document does not provide any suggestions for how to limit, reduce or
transfer capacity, it does provide some baseline data by addressing some fundamental
questions: Who are the developed fishing members? What are their current capacities?
How do they compare to the capacities of developing fishing members? What is the
definition of large-scale purse seiners?
2. Methods
The Glossary (Appendix 1) defines acronyms used in this document.
Quantifying the current capacity of large-scale purse seine vessels in developed
countries that are tRFMO members is not as straightforward as it appears. In our
approach, we took a “snapshot” of the current situation based on data from the RFMOs,
in consultation with some members of the fishing industry and government agencies.
Defining "capacity" is not a simple task, especially in terms of fishing efficiency, but we
took a simplistic approach of identifying numbers of vessels and quantifying their
Suggested citation:
Restrepo, V.R. and F. Forrestal. 2012. A Snapshot of the Tropical Tuna Purse Seine Large-Scale Fishing Fleets at the End of 2011.
ISSF Technical Report 2012-01. International Seafood Sustainability Foundation, McLean, Virginia, USA.

capacity to store fish. Two such measures are commonly used in the literature: Fish
carrying capacity (FCC) and fish hold volume (FHV). Here we conceptualize current
capacity in very general terms without distinguishing between different types of current
capacity such as that being actually realized ("active" capacity) or that which is "latent".
We included data for vessels that are currently authorized to fish, whether they fish or
not.
2.1 Sources of information
Each of the five tRFMOs (CCSBT, IATTC, ICCAT, IOTC and WCPFC) is required to
maintain one or more records (registers) of vessels authorized to fish in their
convention areas. In some cases these records are specific to vessels fishing for a
particular species and in other cases they are general lists of vessels authorized to fish
any species managed by that Commission.
There are several known problems with these lists, including:
- Individual vessels may be authorized in two or more RFMO areas at the same
time; being authorized to fish is not the same as actively fishing.
- The information entered in the lists is, for the most part, reported by
government agencies of the RFMO members. To the degree that not all agencies
have the same ability to monitor and manage their vessels, the information on
the lists is of highly variable quality. Furthermore, different countries may use
different definitions of vessel attributes such as length and tonnage.
- Even though each of the RFMO lists has several mandatory fields, much of the
information is incomplete or absent.
- The RFMO lists are not necessarily updated in real time. The frequency of
updates is not synchronized with the frequency with which vessels change flags,
names, etc.
For the above reasons, it must be borne in mind that the RFMO records are not 100%
accurate at any given point in time. Nevertheless, these lists are improving as the RFMOs
exercise greater scrutiny over them, and they are currently the best source of
information available for tuna fishing fleets at the global level.
The primary sources of information used in this paper were the RFMO vessel records
downloaded from their respective Web sites on December 16, 2011. Other sources of
information were consulted in order to verify duplicate entries, fill in missing data, or
reconcile contradictory information for a given vessel:
- The Consolidated List of Authorized Vessels (CLAV) that is put together several
times each year by the five tRFMO Secretariats. Putting together this consolidated
list involves merging the five lists and using computer algorithms to identify
entries that are likely duplicates. The CLAV is hosted at http://tunaorg.org/GlobalTVR.htm.
The version created on October 10, 2011 was used.
- The Forum Fisheries Agency (FFA) list of vessels "in good standing". Certain
vessels operating in the western Pacific Ocean are not required to be on the
WCPFC record if they do not fish on the high seas or in more than one EEZ. The
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list is published at http://www.ffa.int/node/42; the version corresponding to the
first half of December 2011 was used.
- TURBOBAT, a database of vessels maintained by scientists of the Institut de
Recherche pour le Développement (IRD) and the Instituto Español de
Oceanografia (IEO). The database focuses primarily on European and associated
flag vessels fishing for tropical tunas in the Indian and Atlantic oceans. The
database used was updated December 6, 2011.
- Consultation with several members of the industry and government agencies as
needed.
2.2 Processing
The following steps were taken to compile the list of vessels in this document:
1. Retrieve the CCSBT, FFA, IATTC, ICCAT, IOTC and WCPFC lists and select purse
seine vessels only.
2. Identify duplicates. This involved sorting by Flag and then by name and manually
identifying vessels of the same name or similar name (e.g., "No. 8 XXX" and "XXX
No. 8") and the same characteristics such as size or radio call sign. The CLAV was
consulted as needed.
3. Fill in missing fields (hold volume, fish carrying capacity, LOA) when data were
available from the TURBOBAT file.
4. Set LOA: If several vessel size measurements were available, LOA was set to the
largest value. This is because usually either LOA or LBP, or both, are reported in
the RFMO lists and LOA>LBP.
5. Set GRT: If several vessel tonnage values were available, GRT was set to the
smallest value. This is because usually GRT and GT are recorded in the lists and
GRT

Table 1. Flag codes used in this paper. The column Economy indicates whether a given flag was treated as
a developed economy in this study.
Flag Name Economy Flag Name Economy Flag Name Economy
ANT Netherlands Antilles Other GRC Greece Developed PAN Panama Other
AUS Australia Developed GTM Guatemala Other PHL Philippines Other
BLZ Belize Other HRV Croatia Other PNG Papua New Guinea Other
CHN China, PR Other IDN Indonesia Other RUS Russian Federation Other
CIV Cote d'Ivoire Other IRN Iran Other SLB Solomon Islands Other
COL Colombia Other ITA Italy Developed SLV El Salvador Other
CPV Cape Verde Other JPN Japan Developed SYC Seychelles Other
DZA Algeria Other KIR Kiribati Other SYR Syria Other
ECU Ecuador Other KOR Korea Rep. Developed THA Thailand Other
EGY Egypt Other LBY Libya Other TUN Tunisia Other
ESP Spain Developed MAR Morocco Other TUR Turkey Other
FRA France Developed MEX Mexico Other TUV Tuvalu Other
FSM Fed. States Micronesia Other MHL Marshall Islands Other TWN Chinese Taipei Developed
GBR Great Britain Developed NIC Nicaragua Other USA United States Developed
GHA Ghana Other NZL New Zealand Developed VEN Venezuela Other
GIN Guinea Other OMN Oman Other VUT Vanuatu Other
3. Results
3.1 Global list of purse seine vessels
Merging the RFMO lists, selecting purse seine vessels only, and identifying likely
duplicates, resulted in a total of 1,664 vessels. After following steps 3-5 outlined above
in Section 2.2, this list contained information as follows:
• 83% of the vessels had entries for LOA
• 76% of the vessels had entries for GRT
• 33% of the vessels had entries for FHV
• 19% of the vessels had entries for FCC
Therefore, in terms of choosing whether to measure capacity in terms of FHV or FCC,
using the former would require fewer extrapolations. The estimation of relationships
between different vessel attributes in Section 3.2 is aimed at estimating FHV values for
the vessels that do not contain such information.
In terms of sizes, the vessels with available data showed a bi-modal distribution (Figure
1), with modes around 22.5 and 62.5 meters LOA. Vessel sizes ranged from 5.4 to 116
meters; the smaller values probably correspond to small coastal purse seiners.
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Figure 1. Distribution of purse seine vessel sizes (LOA in m) in the RFMO vessel records.
3.2 Relationships between different vessel attributes
3.2.1 GRT vs LOA
The relationship between GRT (tonnes) and LOA (m) followed a function of the form
(Figure 2):
GRT = 0.0186*LOA 2.5987 (n=975, R 2 =0.90)
There is considerable variability in the relationship, especially for the larger vessels.
Figure 2. Relationship between GRT (tonnes) and LOA (m).
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3.2.2 FHV vs FCC
The relationship between FHV (m 3 ) and FCC (tonnes) was linear (Figure 3):
FHV=1.2269*FCC (n=230, R 2 =0.91)
Figure 3. Relationship between FHV (m 3 ) and FCC (tonnes).
3.2.3 FHV vs LOA
The relationship between FHV (m 3 ) and LOA (m) followed a function of the form
(Figure 4):
FHV = 0.472*LOA 1.873 (n=506, R 2 =0.78)
There is also considerable variability in this relationship. The correlation between FHV
and LOA is not as strong as that between GRT and LOA, or between FHV and FCC. There
is a group of vessels in the 30-40 m size range that appear to be outliers, though this
possibility could not be confirmed using the available data.
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Figure 4. Relationship between between FHV (m 3 ) and LOA (m).
3.2.4 FHV vs GRT
The relationship between FHV (m 3 ) and GRT (tonnes) followed a linear relationship
(Figure 5):
FHV = 524.44+0.6733*GRT (n=324, R 2 =0.60)
For the smaller vessels, some of the data seem to follow a relationship through the
origin (which is logical) while others do not. There is not enough data available to
identify erroneous records.
Figure 5. Relationship between between FHV (m 3 ) and GRT (t).
3.3 Filling in missing values
Taking into consideration the goodness of fit of the various relationships in Section 3.2,
the following approach was taken to fill missing values in the database, aiming to
estimate FHV for all vessels that did not have this information:
1. Fill in LOA: If GRT is available, then use the GRT-LOA relationship in Section 3.2.1
(this was done for 281 vessels). Otherwise, set LOA to average LOA for other
vessels of the same Flag (this was done for 6 vessels).
2. Fill in FHV: If FCC available, use the FHV-FCC relationship from Section 3.2.2 (this
was done for 276 vessels). Otherwise, use FHV-LOA relationship from Section
3.2.3 (this was done for 839 vessels).
3.4 The global tuna purse seine fleet
We estimated that 1,664 purse seine vessels were authorized to fish for tunas at the end
of 2011. Using largely extrapolated data, we estimate that these vessels have a combined
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fish hold volume of 1.03 million cubic meters. The distribution by Flag is given in Table
2. The ratio of vessels flagged to developing versus developed countries is about 1.1.
Table 2. Distribution of tuna purse seiners (all sizes) by flag at the end of 2011. The entries represent the
number of vessels and their estimated combined FHV.
Flag Vessels FHV(m3) Flag Vessels FHV(m3) Flag Vessels FHV(m3)
ANT 3 4400 GRC 19 4036 PAN 17 23006
AUS 12 5109 GTM 6 10402 PHL 139 68352
BLZ 8 9519 HRV 57 13327 PNG 13 9452
CHN 12 16258 IDN 159 48543 RUS 7 6121
CIV 1 871 IRN 8 11660 SLB 5 2147
COL 12 12836 ITA 152 37883 SLV 4 7892
CPV 5 4530 JPN 162 90960 SYC 8 18826
DZA 10 2430 KIR 6 9377 SYR 1 135
ECU 96 72652 KOR 63 71664 THA 4 3950
EGY 1 175 LBY 24 6940 TUN 36 8946
ESP 225 98315 MAR 34 5781 TUR 47 21423
FRA 58 47373 MEX 56 50497 TUV 1 1937
FSM 7 5865 MHL 10 11376 TWN 34 45448
GBR 14 7448 NIC 6 8722 USA 46 59082
GHA 15 17332 NZL 10 6579 VEN 25 28084
GIN 3 2025 OMN 2 413 VUT 21 29136
Total 1664 1029236
Developed 795 473898
Other 869 555338
Oth:Dev 1.09 1.17
3.5 The large-scale purse seine tuna fleet
There are many ways to approach the definition or categorization of large-scale fishing
vessels. One of them is to use the RFMO definitions themselves, which refer to largescale
fishing vessels as being greater than 20 or 24 m LOA, depending on the RFMO.
Since most tuna purse seiners are greater than 20 m LOA (97% according to the data
available to us), we considered a higher threshold that is more related to the ability of
the vessels to make long fishing trips covering large distances. Following consultation
with members of the industry, we chose to use size Classes 5 and 6 as defined by the
IATTC (in tonnes FCC):
Class (1) 0-45 tonnes;
Class (2) 45-91 tonnes;
Class (3) 92-181 tonnes;
Class (4) 182-272 tonnes;
Class (5) 273- 363 tonnes;
Class (6) >363 tonnes.
However, FCC was only available for 19% of the vessels in the RFMO lists. Therefore, we
decided to approach the issue of large-scale based on FHV, which was available for 33%
of the vessels and estimated for the rest as explained above. Using the relationship in
Section 3.2.2 (Figure 3),
273 tonnes FCC ≈ 335 m 3 FHV,
we therefore equated "large-scale" with ≥ 335 m 3 fish hold volume in this study.
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Limiting the list to large-scale vessels as defined here excluded 810 vessels, resulting in
a total of 854 large-scale purse seiners with an overall estimated FHV of 870,000 m 3
(Table 3). Thus, defining large scale as 335 m 3 FHV and larger removed about 49% of
the vessels in numbers, but only removed 15% of the combined hold volume. The
Developing:Developed ratio of capacity increased to 1.28 in terms of numbers of vessels.
Table 3. Distribution of tuna purse seiners (≥ 335 m 3 FHV) by flag at the end of 2011. The entries
represent the number of vessels and their estimated combined FHV.
Flag Vessels FHV(m3) Flag Vessels FHV(m3) Flag Vessels FHV(m3)
ANT 3 4400 GRC 1 386 PAN 17 23006
AUS 7 4110 GTM 6 10402 PHL 76 56933
BLZ 7 9308 HRV 7 3245 PNG 10 8839
CHN 12 16258 IDN 41 23703 RUS 7 6121
CIV 1 871 IRN 8 11660 SLB 5 2147
COL 11 12566 ITA 30 15575 SLV 4 7892
CPV 5 4530 JPN 107 79114 SYC 8 18826
DZA 1 341 KIR 6 9377 THA 4 3950
ECU 69 66711 KOR 58 69392 TUN 9 3597
ESP 48 67423 LBY 4 1662 TUR 33 18308
FRA 41 42708 MAR 1 575 TUV 1 1937
FSM 7 5865 MEX 40 47145 TWN 34 45448
GBR 6 5781 MHL 10 11376 USA 38 57711
GHA 15 17332 NIC 6 8722 VEN 24 27922
GIN 3 2025 NZL 5 6129 VUT 18 28760
Total 854 870092
Developed 375 393778
Other 479 476314
Oth:Dev 1.28 1.21
3.6 The large-scale tropical tuna purse seine tuna fleet
The RFMO lists include purse seine vessels that fish for bluefin tuna either permanently
or sporadically. This is specially the case for the eastern Atlantic and Mediterranean
bluefin stock managed by ICCAT. Since the Commission established strict controls over
vessels starting in 2006, the ICCAT record became populated with many small purse
seiners that fish typically for small coastal pelagics. However they may catch bluefin
occasionally, so they are registered "just in case." In addition, the WCPFC record
includes many Japanese purse seiners which operate north of 20°N and do not usually
target tropical tunas.
In consultation with members from the industry and several agencies, the following
vessels were excluded:
- Vessels flagged to Mediterranean countries (other than Spain and France) and
Great Britain;
- Vessels flagged to Spain and France that are only authorized on the ICCAT
record and are not on the TURBOBAT database.
- Vessels flagged to Japan that are on the WCPFC record but not the FFA record;
Removing these resulted in 678 large-scale, tropical tuna purse seine vessels with a
combined hold volume of 781,000 m 3 (Table 4). Compared to the previous list (all
large-scale purse seiners), these are reductions of 21% and 10% in number of vessels
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and aggregate FHV, respectively. The Developing:Developed ratio of capacity increased
to 1.67:1.0 in vessel numbers.
Table 4. Distribution of large-scale tropical tuna purse seiners (mostly targeting tropical tunas) by flag at
the end of 2011. The entries represent the number of vessels and their estimated combined FHV.
Flag Vessels FHV(m3) Flag Vessels FHV(m3) Flag Vessels FHV(m3)
ANT 3 4400 GIN 3 2025 PHL 76 56933
AUS 7 4110 GTM 6 10402 PNG 10 8839
BLZ 7 9308 IDN 41 23703 RUS 7 6121
CHN 12 16258 IRN 8 11660 SLB 5 2147
CIV 1 871 JPN 36 45614 SLV 4 7892
COL 11 12566 KIR 6 9377 SYC 8 18826
CPV 5 4530 KOR 58 69392 THA 4 3950
ECU 69 66711 MEX 40 47145 TUV 1 1937
ESP 40 63974 MHL 10 11376 TWN 34 45448
FRA 36 40386 NIC 6 8722 USA 38 57711
FSM 7 5865 NZL 5 6129 VEN 24 27922
GHA 15 17332 PAN 17 23006 VUT 18 28760
Total 678 781349
Developed 254 332764
Other 424 448585
Oth:Dev 1.67 1.35
4. Discussion
Using the information available from the tRFMOs we estimate that, towards the end of
2011, there were 1,664 purse seine vessels authorized to fish for tunas worldwide, with
a combined fish hold volume exceeding one million cubic meters. The estimate of the
number of vessels is probably of reasonable accuracy. However, the estimate of fishing
capacity needs to be viewed with caution because it is largely based on extrapolations.
Restricting the list to large-scale vessels, defined here as ≥335 m 3 FHV (approximately
273 tonnes FCC), reduces the number of purse seiners to 854, with a combined FHV of
870 thousand m 3 . Further restricting the list to those large-scale vessels that target
tropical tunas (based on the limited information available) brings the number down to
678 vessels with 781,000 m 3 FHV.
Interestingly, by trimming down the initial list to only large-scale purse seiners that
target tropical tunas, there is a 59% reduction in the number of vessels but only a 24%
reduction in the overall fishing capacity as measured by fish hold volume. This is likely
due to the fact that the RFMO vessel registers contain many small coastal purse seiners
(see Figure 1). Many of these are purse seiners operating in the Atlantic Ocean that
catch bluefin tuna occasionally (purse seining for bluefin in the Mediterranean is only
allowed for one month each year, and presumably most of these target other non-tuna
species during the rest of the year).
The number of large-scale purse seiners targeting tropical tunas estimated here (678
vessels) needs to be seen as an approximation. We have made efforts to exclude vessels
that do not usually target tropical tunas. However, it is possible that in some RFMOs
these vessels could begin to target tropical tunas more actively, depending on their
fishing prospects for other species.
Hamilton et al. (2011) calculated that there are at least 580 industrial-scale tuna purse
seine vessels in the canned tuna industry, based on RFMO registers as of November
2010. This number is lower than the numbers calculated by us for the tropical tuna
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fishery, 678 purse seiners. This difference is mostly due to differences in defining
"industrial-scale" in their paper versus "large-scale" in ours. In their paper, Hamilton et
al. (2011) appear to equate "large vessels" with 250 GRT or greater. Based on the
relationship between FHV and GRT in Section 3.2.4, this would correspond
approximately to 692 m 3 in fish hold volume, which is double the 335 m 3 threshold used
by us.
Tables 2, 3 and 4 present estimates of numbers of vessels and aggregate FHV by flag.
These numbers are likely to change as some vessels re-flag. The number of large-scale
purse seine vessels flagged to developing countries is greater than the number flagged
to developed countries. For large scale tropical tuna purse seiners, the ratio is about
1.7:1. In interpreting this result, it should be kept in mind that many of the vessels
flagged to developing countries may be owned, at least partially, by business interests
from developed countries. A more detailed accounting of ownership would require a
thorough examination of the records vessel-by-vessel, which was beyond the scope of
this study.
In putting together the data used for this study, it became evident that the RFMO records
of vessels would benefit from greater quality control: Often, the same fields contain
conflicting information for vessels that appear in several lists. Also, a lot of information
is missing for many vessels, even when the information is mandatory according to the
relevant RFMO resolutions. These issues should be tackled before a more detailed study
can be conducted.
Acknowledgments
We are grateful to the following individuals who provided information that helped us
compile the various lists: J. Ariz, E. Chassot, M. Goujon, B. Hallman, M. Herrera, M.
McGowan, J. Moron-Ayala, W. Norris, A. Perez, J.P. Rodriguez-Sahagun, M. Takase and R.
Trujillo. In addition, we are grateful to R. Allen, R. Gillett, K. Matthews, S. Jackson, M.
McGowan and J. Moron who commented on earlier drafts of this document.
References
Gillett, R. and A. Lewis. 2003. A Survey of Purse Seine Fishing Capacity in the Western
and Central Pacific Ocean, 1988 to 2003. Gillett, Preston and Associates, 59 pages.
Hamilton, A., A. Lewis, M.A. McCoy, E. Havice, and L. Campling. 2011. Market and
industry dynamics in the global tuna supply chain. Forum Fisheries Agency.
ISSF. 2011. Status of the world fisheries for tuna: Management of tuna stocks and
fisheries, 2011. ISSF Technical Report 2011-05. International Seafood
Sustainability Foundation, McLean, Virginia, USA.
Joseph, J. 2003. Managing fishing capacity of the world tuna fleet. FAO Fisheries Circular
No. 982. Rome, FAO.
Reid C., J.E. Kirkley, D. Squires and J. Ye. 2005. An analysis of the fishing capacity of the
global tuna purse-seine fleet. Pages 117-156 In: Bayliff W. H., J.I. de Leiva-Moreno,
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and J. Majkowski, editors. Second meeting of the Technical Advisory Committee of
the FAO project: Management of tuna fishing capacity: conservation and socioeconomics,
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Appendix 1. Glossary
FCC. Fish Carrying Capacity. The amount of fish, in tonnes, that a vessel can carry. This is
related to the size of the fish wells. However, the actual tonnage carried may vary
depending on the size of the fish and how they are stored. FCC is often measured
as the maximum landings observed for a given vessel.
FHV. Fish Hold Volume: The total measured cubic content of the fish wells, in cubic
meters.
GRT. Gross Register Tonnage: The total measured cubic content of the permanentlyenclosed
spaces of a vessel, with some allowances or deductions for exempt spaces
such as living quarters (1 gross register ton = 100 ft 3 = 2.83 m 3 ).
GT. Gross Tonnage: The volume of all ship's enclosed spaces (from keel to funnel)
measured to the outside of the hull framing.
LBP. Length between perpendiculars: The length of a vessel (loaded) along the
waterline from the forward surface of the stem, or main bow perpendicular
member, to the after surface of the sternpost, or main stern perpendicular
member.
LOA. Length overall: The maximum length of a vessel from the two points on the hull
measured perpendicular to the waterline.
RGL. Registered length: The length of the vessel as registered with the national
authorities. Different countries have different requirements, so RGL could be LOA,
LBP, or other measurements.
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