|
Zootecnia Tropical
Instituto Nacional de Investigaciones Agrícolas Venezuela
ISSN: 0798-7269
Vol. 21, Num. 3, 2002, pp. 261-274
|
Zootecnia Tropical, Vol. 21, No. 3, 2003, pp. 261-274
Management of tuna resources in Venezuela
Manejo del recurso atunero en Venezuela
Ana Cabello1*,
Jesus Marcano1, Mirle Narváez2, Omelys Silva 2,
Antonio Gómez 2, Bertha Figuera1, Osmicar Vallenilla1 y
Hebel Salazar1
Code Number: zt03017
ABSTRACT
Venezuela is considered an important tuna producer because
its fleets operate in the Pacific and Atlantic Oceans and land about 80000
t/year. This landing is oriented 65% towards export, 20% to the canning industry,
and 15% for direct consumption as fresh fish. The fleet captures five species
of tuna, among other smaller scombrid species. All tuna species are highly
migratory and shared among several countries. Tuna is one of the fish items
with higher demand among consumers. Because of its importance, several aspects
of its exploitation, like fishery, bromatological characteristics, and processing
have been studied. Because is a species of high commercial importance with
large nutritional value. This paper studies the relationship among catch, commercialization,
and sanitary aspects, which are involved in the use of tuna as a food source
and as an item for export. Currently, the fishery shows a decreasing trend
in the landings of all tuna species. The bromatological evaluation confirmed
a protein content of 23.65 to 24.78 % and low levels of heavy metals like Hg,
Cd, Cu, and Zn. Since the current legislation in Venezuela regulating tuna
byproducts only establishes critical levels for Hg, its revision is needed
to incorporate other potentially hazardous heavy metals.
Key words: Tuna, management, bromatology, processing, nutritional
value.
RESUMEN
Venezuela es considerada como un importante productor de atún
porque su flota faena en los Océanos Pacífico y Atlántico y aporta 80.000 t/año.
Esta producción se distribuye en 65% para exportación, 20% a la industria conservera
nacional y 15% al consumo fresco. Todas las especies de atún son altamente
migratorias y compartidas con otros países. El atún es uno de los peces con
más demanda por parte de los consumidores. Debido a su importancia, varios
aspectos de su explotación, como la pesquería, las características bromatológicas
y procesamiento, se ha estudiado. Siendo estas especies de alta importancia
comercial, con gran valor nutricional, se estudia la relación entre captura,
comercialización y aspectos sanitarios que están involucrados en el uso de
atún como fuente de alimento y como un insumo para la exportación. Para lograr
estos objetivos se realizaron muestreos en puerto y se recolectaron muestras
que fueron analizadas en el Laboratorio de Tecnología de Alimentos utilizando
métodos físico-químicos y bioquímicos como la cromatografía de absorción atómica
para la determinación de metales pesados. Actualmente, la pesquería muestra
una tendencia decreciente en los desembarcos de todas las especies de atún.
La evaluación bromatológica confirmó un contenido de proteína entre 23,65 y
24,78% con bajos niveles de metales pesados como Hg, Cd, Cu y Zn. En la legislación
actual en Venezuela la regulación de atún por productos sólo establecen los
niveles críticos para Hg, su revisión es necesaria para incorporar otros metales
pesados potencialmente peligrosos.
Palabras clave: Atún, manejo, bromatología, procesamiento, valor
nutricional.
INTRODUCTION
In Venezuela, tuna is one of the three most important commercial
fish resources due to their annual landings, fleets with the Venezuelan flag
operating in both, the Pacific and Atlantic oceans, their installed infrastructure
for processing, the number of generated jobs, and the high incomes resulting
from their commercialization. In addition, there is a wide acceptance of the
different tuna species among the Venezuelan consumers, due to tuna good taste
and its nutritional quality. In addition, there is a high demand in the international
markets. Artisans and industrial methods perform tuna fisheries (Marcano, 2002).
The industrial tuna fleet is the most relevant, and operates in the Atlantic
and Pacific Oceans in front of the coasts of Ecuador and Colombia. This fleet
landed more than 139,000 t in 2001, which is considered an extraordinary catch.
Artisan fisheries operate inshore with vessels of little autonomy; their landings
reach near 6,000 t per year and are sold as fresh fish or dry-salted.
Tuna is one of the resources that are processed by the Venezuelan
canning industry. Seventy percent of the national landings (about 57,000 t)
are processed this way, while 20% (about 20,000 t) is consumed in fresh, and
11% (about 8,250 t) is exported either completely or as loins (Cabello et
al. 2002).
Venezuela is a member of the International Commission for
the Conservation of Atlantic Tunas (ICCAT) and the Interamerican Tropical Tuna
Commission (IATTC). These organizations evaluate the status of tuna and associated
resources, and regulate their fishing in the Atlantic and Eastern Pacific Oceans,
respectively. To accomplish these goals, they use information on annual catch
and effort of all the fleets. The migratory nature of tuna and associated resources
(sharks, billfish and marine mammals, incidentally captured along with tunas)
makes them to be considered as international resources.
In 1988, Gaertner et al. set up a system for continuous
collection of data on catch and effort using logbooks in industrial tuna vessels.
On the same year, Pagavino et al. studied the evolution of the tuna
surface fishery, while Eslava (1990) studied the Venezuelan long line tuna
fishery in the Caribbean Sea. Marcano et al. (1994) described the biometric
relations of yellowfin tuna landed by the Venezuelan long line fishery. All
these studies have contributed to a better understanding of the tuna fishery
in the country.
The objective of this study is to characterize the tuna fishery,
considering the composition of the fleet, the type of fishing gear, operating
zones, and the analysis of the catch and trends of the capture per unit of
effort CPUE. The bromatological and toxicological characteristics of tuna meat
were also evaluated, due to the importance of this raw material for the canning
industry and for the diet of the Venezuelan people.
MATERIALS AND METHODS
The used information came from logbooks, landing checks, multispecific
samplings in the harbors, historical databases on catch and effort maintained
by INIA, and field samples that were analyzed in the Food Technology Laboratory
of INA, Cumaná. The multispecific sampling was made at random and stratified
in two levels; the primary units were the sets and the secondary the fish.
The proportion and size structure of each species in the landings were evaluated.
The total size of the sample was calculated using weight – length relationships
for each species (Pagavino, 1990) and then extrapolated to the weight of the
whole container of the vessels where the sample came from.
Biological samples were collected from only two species of
tuna, Thunnus albacares and Thunnus obesus, which are considered
the most important by the canning industry. Between 6 and 12 samples were collected
once a month for 9 months from commercial catches of two canning industries
located at Cumaná, Sucre state, Venezuela. Each sample represented a pool of
muscular tissue from different parts of the animal. Due to the high value of
large size tunas, and since skin or muscle cuts decrease the value of animals
aimed at the export market, tissue samples were obtained from middle size animals,
in the range 65 to 1,200 cm fork length. Samples were taken to the Laboratory
of Food Technology of INIA at Cumaná to be analyzed. The methods employed were
those internationally recommended for the determination of proximal composition
and heavy metals in food. The analyses of protein, humidity, ash, fat and salt
contents followed A.O.A.C. (1994). Analyses of pH and total basic volatile
nitrogen (TBVN) were performed according to the norm COVENIN 1315-79 (COVENIN
1979). Energetic value was estimated according to Deulofeu and Marenzi (1960).
Mercury was analyzed according to Armstrong and Uthe (1971) and Cd, Cu and
Zn were analyzed according to Leonard (1971).
Values of the physical-chemical evaluations were analyzed
using a two way ANOVA procedure with replication (Sokal and Rohlf, 1995), in
order to establish the significance of the variations between samples from
the Atlantic and Pacific Oceans. A Duncan a posteriori test was used
when required.
RESULTS AND DISCUSSION
Venezuela is considered an important tuna producer and has
a fleet of 26 purseiners operating in the Eastern Pacific Ocean and 55 vessels,
among purseiners, bate boats and long liners, operating in the Western Atlantic
Ocean. The proportion of tuna landings from the Pacific Ocean accounts for
63% of the total catch, while the remaining 37% come from the Atlantic Ocean.
During the last twenty years, catches from the Pacific Ocean have fluctuated
from 9,000 t to 109,000 t, and catches from the Atlantic Ocean between 9,000
t and 41,000 t (Figure 1). In 2001, both fleets landed a record catch of 139000
t.
The fleet operating in the Pacific Ocean comprises only a
purseiner, and has larger vessels (1,200 to 1,600 gross tonnages) with modern
technology to search and catch schools of tuna. This fleet operates between
the parallels 40 °N and 40 °S. In comparison, the fleet operating in the Atlantic
Ocean
comprises 31 long line vessels, 14 bate boats, and 10 purseiners
(600 GT). They operates between the parallels 3° and 20° N, and between meridians
50° and 75° W. Landings from the Pacific Ocean have a clear increasing trend,
whereas those from the Atlantic Ocean by fishing gear, show stability since
1980 for bate boats and large variations for purseiners, with a decreasing
trend, except for the year 2001 (Figure 2).
Fifteen species are landed, among tunas and tuna-like species,
most being captured either with purseine net or hooked with live bate (Table
1). The yellowfin tuna, Thunnus albacares, represents 66.4% of the landings
from the purseiners, 84.2% from the bate boats and 48.4% from the long
liners. The latter and skipjack tuna, Katsuwonus pelamis, are the species
with the greatest importance for the canning industry and for export, and were
chosen as samples for bromatological and toxicological characterization.
|
Table 1. Tuna species landed by the Venezuelan fleet |
|
|
Scientific name |
Common name |
Main Fishing gear |
|
|
Thunnus albacares |
Yellowfin tuna |
Purseine, long line, live bait fishing |
|
Katsuwonus pelamis |
Skipjack |
Purseine, live bait fishing |
|
Auxis thazard |
Frigate fish |
Purseine, long line, live bait fishing |
|
Thunnus alalunga |
Albacore |
Purseine, long line, live bait fishing |
|
Thunnus obesus |
Big eye tuna |
Purseine, long line, live bait fishing |
|
Thunnus alanticus |
Blackfin tuna |
Purseine, long line, live bait fishing |
|
Sarda sarda |
Bonito |
Long line |
|
|
Table 2. Average results of the proximal composition
of two species of tuna from the Pacific and Atlantic Oceans.
|
|
|
Parameters |
Species |
|
|
Katsuwonus pelamis |
Thunnus albacares |
|
|
Atlantic |
Pacific |
Atlantic |
Pacific |
|
|
Protein % |
24.91 |
24.39 |
24.65 |
23.08 |
|
Humidity % |
70.86 |
67.90 |
71.99 |
71.57 |
|
Fat % |
0.39 |
0.32 |
0.34 |
0.52 |
|
Ash % |
2.28 |
3.04 |
2.00 |
2.30 |
|
The proximal composition of fish varies according to species
and among them according to age, sex, physical condition or feeding (Kodaira,
1991). One of the supports for choosing a raw material for a technological
process is the knowledge of nutritional parameters that helps taking decisions
about proper conservation treatments that need to be applied. The proximal
composition of the two species of tuna evaluated in this work showed a high
protein content in meat (24.65% SKJ and 23.86% YFT; Table 2). There were no
significant differences in the protein content between species, ocean of origin,
or the interaction between these two variables (P>0.05). The variation of
fat content showed similar results for species and ocean of origin (P>0.05),
but the interaction between them was significant (P<0.05). The high protein
content allowed its classification as lean meat, with a fat content lower than
5% for the evaluated samples. It is recommended that a 3 years period of sampling
be performed in order to determine the variation of nutritional parameters,
particularly the fat content, which is a parameter of great interest for commercialization
and canning processes.
Ash content showed significant differences between species
(P<0.05), but there were no significant differences between oceans or interaction
(P>0.05). The high-recorded ash values (average 6.17%) could be associated
to a high content of salt. This is due to the conservation methods of tuna
on board, which use low temperature brine by mixing seawater, salt and ice,
exposing the fish to a very high concentration of salt during the long period
of the campaign, resulting in absorption of the salt by the tuna meat.
Water content, expressed as humidity, showed significant differences
between species (P<0.05), but there were no significant differences between
ocean of origin or interaction (P>0.05).
Quality parameters, like pH and total volatile basic nitrogen
(TVBN), showed a wide range of variation. Fish under this condition can be
classified into the Type II of commercial categories, since Type I would be
fish of recent capture that has not been preserved on ice or frozen (López,
1985). This condition is due probably to the long periods tunas remain frozen
on board and the lack of control of the freezing process. We recommend improvements
in the methods and temperatures used for storing the tuna catch.
The range of pH values for skipjack from the Pacific Ocean
was 5.82 to 6.71 and 5.57 to 6.76 for the fish from the Atlantic Ocean. The
range of pH for yellowfin tuna was 5.92 to 6.78 (Pacific Ocean) and 5.36 to
6.79 (Atlantic Ocean). The use of salt as solute to speed up the freezing process
has an effect upon pH variation. Premoli (1986) reported a pH value of 6.4
for very fresh fish, while Gómez and Cabello (1994) reported a pH value of
5.4 for frozen tuna delivered to cannery. These authors indicated that the
transportation means between harbors and the storage facilities or cannery
severely affected the freshness of the raw material. In occasions, frozen tuna
are transported in trucks without cover, exposing the fish to direct sun light
and high temperature. Nowadays the use of covers in the trucks is common as
well as the use of refrigerated trucks for transportation of frozen tuna.
The values for TVBN were below the maximum allowed for human
consumption (125 ¼g/100 g dry weight), indicating that the raw material
was in good condition to be used in the canning process. However, TVBN values
were variable in both species from either ocean, and were considered high for
fresh raw material. This condition is associated with the long campaigns leading
to storage periods longer than three months. Gómez (1994) reported that environmental
temperature plays an important role in the increases of non-protein-nitrogen
compounds in conserved fish meat.
The energetic value of the two species of tuna was 113.16
cal/g for T. albacares and 109.70 cal/g for K. pelamis. These
values associate tuna meat to low calorie diets, because of the low fat content.
The condition of migratory species forces them to spend large amounts of energy
into motion, thus lowering the fat stored in the meat.
The toxicological evaluation was made due to the growing concern
on increasing pollution of marine coasts and oceans, which affect the life
of fish living in them and could threat the safe commercialization and consumption
of tuna meat. Moreno (1998) commented on the growing interest in the study
of heavy metals effect on marine organisms and the fact that trace quantities
of them (approximately 50 ¼g/kg) are essential for a large number of organisms,
including plants. COVENIN (1981), in its norm 1766-81 (in revision), refers
as maximum limits for content of Hg, Cd, and Cu values of 0.5, 0.1, and 10 ¼g/kg,
respectively. Zinc has not been included as contaminant yet. Tunas, in their
continuous migration among coastal waters and oceans, are particularly susceptible
to accumulate heavy metals and other pollutants. For tunas from the Pacific
and Atlantic Oceans, the detected concentration of Hg, Cu, and Zn were below
the permissible limits in Venezuela for human consumption (Table 3). Only the
concentration of Cd in two sampling periods was above the permissible limits
for human consumption. This situation represents an alert, so effort must be
increased to reduce discharges of industrial wastes into the oceans.
|
Table 3. Detected concentration of heavy metals in
meat of T. albacares and K. pelamis from the Pacific
and Atlantic oceans. |
|
|
Heavy metal, ¼g/g DW |
Ocean |
|
|
Pacific |
Atlantic |
|
|
Hg |
0.09 – 1.20 |
0.06 – 1.00 |
|
Cd |
0.04 – 0.43 |
0.08 – 0.34 |
|
Cu |
1.18 – 2.41 |
0.16 – 3.20 |
|
Zn |
0.15 – 3.20 |
10.38 – 41.50 |
|
CONCLUSIONS
- Tuna production in Venezuela represents 29% of total fishery landings and
is the first item in foreign income from exports.
- Tuna and tuna-like species in Venezuela are resources with a high interest
for the fishery sector. Seventy per cent of the landings are used in industrial
canning processes, 10% of the landings are frozen and exported, while the
remaining 20% is consumed in fresh. Due to their nutritional value, they
can recommended as a diet rich in protein diet and low in fat, with an average
protein content of 24.26% and fat content of 1.93%.
- Freshness (bromatological) and toxicological (heavy metals) conditions
of the evaluated tuna were acceptable for consumption and canning. However,
conservation processes on board should be adjusted to decrease the salt content
of tuna meat and the pH and TVBN values.
-
Traces of heavy metals detected (Hg, Cd, Cu, and Zn) have
the potential to be associated with severe human diseases. This represents
an alert for an in depth surveillance of these resources that is valuable
for the fishing industry and appreciated by consumers.
ACKNOWLEDGEMENTS
The authors appreciate the assistance of J. Alió in the technical
revision and translation of this document. We also thank the help received
from the companies FIPACA and Alimentos Margarita C.A., for providing the tuna
samples and companies spaces for their processing.
BIBLIOGRAFÍA
- A.O.A.C. 1994. Oficial Methods of Analysis 13th ed. Washington
D.C U.S.A.
- Armstrong, F. A. y J. F. Uthe. 1971. Semi-automated determination
of mercury in animal tissue. Atomic Absorption Newsletter. Slavin, S. (ed.).
The Perkin-Elmer Corporation, U.S.A. Vol 10, pp 101 - 103.
- Cabello, A., B. Figuera, J. Marcano y O. Vallenilla. 2002.
Aprovechamiento e industrialización del atún y otros grandes pelágicos. Memoria
del Taller "Aprovechamiento e industrialización de atún y otros grandes
pelágicos". ICTA-UCV. Caracas, Venezuela.
- Covenin. 1979. Alimentos. Determinación de pH (Acidez iónica).
1315-79. Comisión Venezolana de Normas Industriales. Caracas, Venezuela.
- Covenin 1981. Atún en conserva (1766-81). Comisión Venezolana
de Normas Industriales. Caracas, Venezuela.
- Deulofeu, V. y A. Marenzi. 1960. Curso de Química Biológica.
8ª Edición. Editorial Ateneo, Buenos Aires, Argentina. 825 p.
- Eslava de G., N. 1990. Análisis de la pesquería venezolana
de atún con palangre en el Caribe y el océano Atlántico. Tesis de Maestría.
Instituto Oceanográfico. Universidad de Oriente. Cumaná, Venezuela.
- Gaertner, D., C. Medina-Gaertner.y L. Martínez. 1988. Instalación
de un sistema de bitácoras para la pesca atunera de superficie en Venezuela
y análisis de los primeros resultados. Coll. Vol. Sci. Pap. ICCAT. 28:130-140.
- Giménez, C. 2002. Situación atunera mundial y el caso venezolano.
Memoria del Taller "Aprovechamiento e industrialización de atún y otros
grandes pelágicos". ICTA-UCV. Caracas, Venezuela.
- Gómez, A. y A. Cabello. 1994. Determinación de nitrógeno básico
volátil total (NBVT) durante el procesamiento de atún en conserva. Acta Científ.
Venez.. 45 (Sup.1): 310.
- Gómez, A. 1994. Determinación de nitrógeno básico volátil
total (NBVT) en los túnidos procesados industrialmente en Alimentos Margarita
C.A., Mariguitar, Estado Sucre. Tesis de Grado. Universidad de Oriente. Departamento
de Biología. Núcleo de Sucre. Cumaná, Venezuela.
- Kodaira, M. 1991. Composición química y cambios post-morten
en pescado, crustáceos y moluscos. Curso-Taller "Avances en biotecnología
de organismos marinos de importancia comercial" 31 p.
- Leonard, N. 1971. The determination of copper in fish tissues
by atomic absorption spectrophotometry. En: Atomic Absorption Newsletter.
Sabina Slavin (ed.). The Perkin-Elmer Corporation, U.S.A. pp. 84
- 85.
- López, F. 1985. XV. Normas para valorar el atún congelado
a bordo. Curso "Avances en procesamientos de productos pesqueros" Seminarios
del Postgrado en Ciencia y Tecnología de los Alimentos, Universidad Central
de Venezuela, Caracas.
- Marcano, J., H. Salazar y L. Astudillo. 1994. Relaciones biométricas
del atún aleta amarilla Thunus albacares, desembarcado por la flota
palangrera venezolana. Coll. Vol. Sci. Pap. 42(2):310-313.
- Marcano, J., X. Gutiérrez, H. Salazar y M. Márquez. 2002.
Pesquería Industrial de túnidos. Memoria del Taller "Aprovechamiento e
industrialización de atún y otros grandes pelágicos". ICTA-UCV. Caracas,
Venezuela.
- Pagavino, M. 1988. Evolución reciente de la pesquería atunera
de superficie en Venezuela. Acta Cientif. Venez. 38(Supl. 1):61.
- Pagavino, M. 1990. Pesquería atunera y caña de la flota venezolana.
Tesis de Maestría. Instituto Oceanográfico. Universidad de Oriente. Cumaná,
Venezuela.
- Premolí, A. 1986. Estabilidad de la cachama (Colossoma
macropomum) almacenada en refrigeración. Trabajo de Grado. Escuela de
Biología. Facultad de Ciencias, Universidad Central de Venezuela, Caracas.
- Silva, O. y A. M. Cabello. 1998. Contenido de metales en túnidos.
Acta Científ. Venez., 49(Supl. 2):49.
- Sokal, R. y F. Rohlf. 1995. Biometry. 3ra Ed. W.H.
Freeman, New York, 887 p.
Copyright 2003 - Zootecnia Tropical.
|
