Reproduction of the jumbo flying squid, Dosidicus gigas Orbigny, 1835 Cephalopoda
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
SCI. MAR., 61 (Supl. 2): 33-37 SCIENTIA MARINA 1997
ECOLOGY OF MARINE MOLLUSCS. J.D. ROS and A. GUERRA (eds.)
Reproduction of the jumbo flying squid,
Dosidicus gigas (Orbigny, 1835) (Cephalopoda:
Ommastrephidae) off Peruvian coasts*
RICARDO TAFUR and MIGUEL RABÍ
Instituto del Mar del Perú (IMARPE), P.O. Box 22, Callao, Peru.
SUMMARY: A sample of 17,683 individuals of Dosidicus gigas was collected between 1991 and 1994 from Japanese and
Korean fishery boats by on-board Peruvian observers. On the basis of a modification of the Nesis (1970) macroscopic scale,
four stages of maturity for females and males were assessed. The mean mantle length at first maturity was 32 cm for females
and 28 cm for males. For the period 1991 to 1994, the spawning peaks were identified using three different methods; the
spawning progression (variation of the III stage over time), variation of the nidamental gland index ((LNG/ML)×100) and
the gonadosomatic index (Gonad weight × 108/ML3). Spawning extends throughout the year, but the most important spawn-
ing peak occurs during October to January, without variation between the years of study. Secondary peaks were identified
during July and August. The variation in nidamental gland length in relation to mantle length provides an acceptable index
to indicate when spawning occurs.
Key words: Dosidicus gigas, Cephalopoda, Ommastrephidae, Southeast Pacific.
RESUMEN: REPRODUCCIÓN DEL CALAMAR VOLADOR Dosidicus gigas (ORBIGNY, 1835) (Cephalopoda: Ommastrephidae)
EN AGUAS DE PERÚ. – Una muestra total de 17,683 individuos de Dosidicus gigas fue recolectada durante el período 1991 a
1994, por observadores peruanos a bordo de las embarcaciones calamareras japonesas y coreanas que operan en aguas perua-
nas. Sobre la base de una modificación de la escala macroscópica de madurez de Nesis (1970) se estudiaron cuatro estadios
de madurez para hembras y machos. La longitud media del manto para la primera madurez se estimó en 32 cm para las hem-
bras y 28 cm para los machos. Para el período de 1991 a 1994 se identificaron los picos de desove utilizando tres métodos:
seguimiento de la progresión del desove (variación de la incidencia del estadio III en el tiempo), variación del índice de la
glándula nidamental ((LNG/ML)×100) y el índice gonadosomático (peso de la gónada × 108/ML3). El desove ocurre duran-
te todo el año, pero se presentan dos máximos, que acontecen de octubre a enero, sin observarse variación en el período
estudiado. Máximos secundarios de menor intensidad fueron identificados entre julio y agosto. La variación de la longitud
de la glándula nidamental en relación con la longitud del manto provee un aceptable índice para señalar la ocurrencia del
desove.
Palabras clave: Dosidicus gigas, Cephalopoda, Ommastrephidae, Pacífico suroriental.
INTRODUCTION the oceanic waters adjacent to upwelling zones
(Nesis, 1970, 1983; Ehrhardt, 1991; Ehrhardt et al.,
The Jumbo flying squid Dosidicus gigas 1983, 1986).
(Orbigny, 1835) is widely distributed in the eastern To date, this ommastrephid squid represents the
Pacific. Its distribution seems to be associated with most important pelagic invertebrate fishery in Peru.
Large scale fishery was initiated in 1991 with the
arrival of the Japanese and Korean jigging fleet.
*Received May 1996. Accepted December 1996. Before then the species was studied from samples
REPRODUCTION OF DOSIDICUS GIGAS OFF PERUVIAN COASTS 33collected in the trawling fisheries where D. gigas Previous studies on the reproduction patterns of
was caught as by-catch, from the small scale hand- related species of Ommastrephids indicate that some
jigg fishery, and from samples collected in the of them present multiple spawning (Harman et al.,
Rhyusho Maru #25 cruise in 1980 which was the 1989) defined as the intermittent terminal spawning
first cooperative Peruvian-Japanese cephalopod of semelparous animals with somatic growth occur-
cruise using automatic jigging machines (Benites rence between separate spawning events (Rocha et
and Valdivieso, 1986). al., 1996).
During the 1980’s, the D. gigas catch was a signi- Our preliminary results of maturity progression
ficative portion of the total catch of the former Soviet show different groups present in samples taken in
Union trawling fleet which operated inside and out- the same fishery area. The reproductive strategy pat-
side the Peruvian economic zone. The specific tern is not yet clearly defined.
research in Peru on D. gigas started with the second
cooperative Peruvian-Japanese exploratory cruise
(Shinko Maru #2). The study and resource survey MATERIALS AND METHODS
were developed between November and December of
1989 (JAMARC, 1991; Rubio and Salazar, 1992). A sample of 17,683 individuals of Dosidicus
D. gigas has been reported in the commercial land- gigas (8,807 females and 8,876 males) was collect-
ings since 1964, representing 30% of the total ed from April 1991 until December 1994 from the
Peruvian cephalopod catch (MIPE, 1982). Between Japanese and Korean jigging fleet by the Peruvian
1991 and 1994 the total catch for the whole period was on-board fishery observers. The mantle length range
450,000 t obtained by the Japanese and Korean large was from 120 to 890 mm for both sexes. Samples of
scale fleet. This fishery is managed only by quantity 10 males and 10 females were collected by each
quotas in tons per boat and per the total fleet, quotas observer at every boat and fishery trip. The samples
being awarded by tender. The fishery is an important were frozen on-board and were analyzed in the lab-
economic income for the Peruvian government. oratory after defrosting at room temperature.
To date, the most important management restric- Mantle length (ML), total weight (TW), mantle
tion is the establishment of a protection zone into the weight (MW), ovary weight (OW), oviduct weight
30 nautical miles adjacent to the Peruvian coast, (OvW), nidamental gland weight (NGW), nidamental
without any other biological parameters, such as gland length (NGL) were registered for each female.
size or reproduction stages, being considered for the Maturity was assessed using a macroscopical maturi-
management. The aim of this paper is to show pre- ty scale and presence of copulation marks on the buc-
liminary results from the monitoring of the variation cal membrane was also recorded. The following data
and periodicity of the reproductive cycle of D. gigas were recorded in males: Mantle length (ML), total
within the sampled Japanese and Korean fleet fish- weight (TW), spermatophoric complex weight (SW),
ing range of its wide distribution. testicle weight (GW) and spermatophoric sac weight
Previous studies about the reproduction of D. (SSW). A macroscopical maturity scale was
gigas were developed for the northern portion of its employed to assess male maturity.
distribution (Nesis, 1970, 1983; Ehrhardt et al., For the macroscopical maturity scale a modifica-
1983, 1986; Ehrhardt, 1991). D. gigas was consid- tion of the Nesis (1970) macroscopical scale was
ered with other ommastrephids as an essentially developed: one additional stage for the males scale
oceanic spawning species (Nigmatullin and was considered and the 3rd and 4th stage for the
Laptikhovsky, 1994). females scale were established with accuracy (Table
Nesis (1970) defines the first specific maturity 1). The size at first maturity was calculated using a
scale for D. gigas, and also proposes the possibility subsample for the cumulative percentage for both
to find, at least, three different groups, able to be dis- sexes.
tinguished by the photophore distribution due basi- The spawning peaks were identified by 3 differ-
cally to the geographic isolation between the ent methods:
Mexican and Central America groups in relation to 1) Spawning progression: Based on the propor-
the South American ones. The present maturity pro- tion of the monthly occurrence of the 3rd stage of
gression study could give more evidence to support maturity in males and females.
the genetic isolation theory and show the spawning 2) Nidamental gland index (NGI) (modified after
seasons in the Peruvian region. Soeda et al., 1959):
34 R. TAFUR and M. RABÍTABLE 1. – Macroscopical maturity scale used in Dosidicus gigas RESULTS
Males Females The maximum mantle length observed was 725
mm for males and 890 mm for females, and the
I. Immature I. Immature
Testis transparent. Sperma- Nidamental gland short and minimum observed was 120 mm for males and 133
tophoric organ thin and translucid. Ovary transpa- for females. The mean mantle length at first matu-
transparent. rent.
rity for the total sampling period (1991-1994), was
II. Maturation II. Maturation
Cream testis. Spermato- Cream nidamental glands. 288 mm for males and 322 mm for females (Figs.
phoric sac with some white Granulated ovary. 1 and 2).
particles.
III. Mature Spawning extends throughout the year, but the
III. Mature Larger nidamental glands, most important spawning peak occurs from October
Spermatophoric sac full of (20%-50% of the mantle
spermatophores. Testis cavity). Ovary full of eggs, to January, significatively high in November, with-
white and bigger. yellow colored. out variation between the years of study (Figs. 3 and
IV. Spawned IV. Spawned 4). Secondary peaks were identified from July to
Spermatophoric sac flaccid Nidamental glands flaccid
with some sperm residuals. and reduced. Oviduct with August.
Testis streaked. some eggs. The variation of the NGI in relation to the ML
provides an acceptable indication of when spawning
occurs (Fig. 5). As a intermittent or multiple spawn-
ing species, the females seems to mature at two dif-
NGI = NGL x100 , ferent modal sizes, hence perhaps at two different
ML ages. The males mature in the same manner but ear-
lier than the females (Figs. 3 and 4).
where NGL is the nidamental gland length and ML
is the mantle length.
3) Gonadosomatic index (GSI) (modified after
Araya and Ishii, 1972):
8
GSI = Gw.10
3
ML
where Gw is the gonad weight.
Maturity coefficient (MCO) and nidamental
gland index (NGI) were used in order to observe the
relationship between the mantle length and the
FIG. 1. – Mean mantle length at first maturity in D. gigas females,
reproductive stage (Boyle and Ngoile, 1993). The during the 1991-1994 study period.
MCO for females is expressed by the equation:
(Gw + OOG).100 ,
MCO =
TW – (Gw + OOG)
where OOG is the weight of oviduct + oviducal
gland, and TW is the total weight. The MCO for
males is expressed by the equation:
(Gw + SW) ×100
MCO = ,
(TW – (Gw + SW))
where SW is the spermatophoric complex weight FIG. 2. – Mean mantle length at first maturity in D. gigas males,
and Gw is the weigth of the testicle. during the 1991-1994 study period.
REPRODUCTION OF DOSIDICUS GIGAS OFF PERUVIAN COASTS 35FIG. 3. – NGI and GSI variation from April 1991 to December 1994.
The most important spawning peaks are marked with arrows.
FIG. 6. – Relationship between maturity coefficient (MCO) and
mantle length. Different size at mature aggregation groups
observed during the 1991-1994 study period.
DISCUSSION
FIG. 4. – Maturity stages III + IV proportion (%) variation from The spawning and capsule laying in this species
April 1991 to December 1994. The most important spawning peaks are, until now, not well documented events. Only
are marked with arrows.
some incidental spawns in on-board tanks have been
observed, probably containing unfertilized eggs laid
The same pattern is shown by the maturity coef- as defensive strategy (personal observation).
ficient in males and females (MCO) in relation to The use of gonadosomatic indices can make the
the ML (Fig. 6 a, b). This reproductive pattern was spawning evident, as well as indicate the geograph-
observed in some specimens within the sample, ic area where it occurs and the variations of the
being more evident during 1992 and early 1993. mean mantle size of maturity. For this study data
obtained at the large scale fleet operating inside the
Peruvian Economic Zone were used; with this infor-
mation we could only study a fraction of the popu-
lation that had been selected by the jigging equip-
ment within the areas with the highest concentra-
tions, where the commercial fleet was aggregated.
Samples from other areas, like the adjacent coastal
area (30 nautical miles) and outside the Peruvian
Economic Zone (200 nautical miles) oceanic area
were scarce and non significant.
From the results of this paper we can extract
two possibilities. Firstly, multiple spawning in D.
gigas is possible based on the observation of the
maturity stage and nidamental gland length varia-
FIG. 5. – Relationship between nidamental gland index (NGI) and
mantle length, two group aggregations observed during the 1991- tion in shorter and longer individuals, indicating
1994 study period. the possibility of somatic growth between the
36 R. TAFUR and M. RABÍintermittent spawning for the same population ACKNOWLEDGMENTS
individuals. The second possibility implies the
existence of two population groups differing in The authors acknowledge with thanks several
size at maturity, a small-sized, early-maturing reviewers for the critical reading of the manuscript
population and another group of large-sized, late- and editorial work. We also thank Dr. Angel Guerra
maturing animals, mixed in the same fishery area. for his valuable help and suggestions.
This possibility is supported by a similar case, the
Indo-Pacific ommastrephid squid Sthenoteuthis
oualaniensis (Nesis, 1993). The morphological REFERENCES
differentiation of the mature females to define iso-
Araya, H. and T. Ishii. – 1972. Population structure of common
lated populations was mentioned by Nesis (1970, squid in the waters around Hokkaido. Res. Rep. Tech. Couns.
1983) for D. gigas, showing at least three groups Agr. For. Fish., 57: 192-205.
Argüelles, J. – 1996. Crecimiento y reclutamiento del calamar
based on geographical isolation. In our case, all gigante Dosidicus gigas en el Perú (1991 a 1994). Inf. Progr.
the samples were collected in the same fishery Inst. Mar del Perú, 23: 1-14.
Benites, C. and V. Valdivieso. – 1986. Resultados de la pesca
area, inside the authorized Peruvian Economic exploratoria de 1979/80 y desembarque de cefalópodos pelági-
Zone (30-200 miles off Peruvian coasts) due prob- cos en el litoral Peruano. Bol. Inst. Mar del Perú, 10: 107-139.
Boyle, P.R. and M.A.K. Ngoile. – 1993. Assessment of maturity state
ably to a major environmental factor, such as El and seasonality of reproduction in Loligo forbesi (Cephalopoda:
Niño phenomena. Loliginidae) from Scottish waters. In: T. Okutani, R.K. O’Dor and
T. Kubodera (eds.), Recent Advances in Cephalopod Fisheries
Recent growth and recruitment studies Biology, pp 37-48. Tokai University Press, Tokai.
(Argüelles, 1996) based on D. gigas mantle length Ehrhardt, N.M. – 1991. Potential impact of a seasonal migratory
jumbo squid (Dosidicus gigas) stock on a Gulf of California
frequencies from the same database we used in sardine (Sardinops sagax caerulea) population. Bull. Mar. Sci.,
this work support the separate population theory. 49: 325-332.
Ehrhardt, N.M., P.S. Jacquemin, F. García, G. González, J.M. López,
These studies show the intrusion of a population B. Ortiz and A. Solís. – 1983. On the fishery and biology of the
group in 1992 and early 1993 with different giant squid Dosidicus gigas in the Gulf of California, Mexico. In:
J.F. Caddy (ed.), Advances in assessment of world cephalopod
growth pattern, and long individuals (700 - 900 resources, pp 306-340. FAO Fish. Pap. n 231.
mm) with faster growth than short ones. This Ehrhardt, N.M., A. Solís, P.S. Jacquemin, J. Ortiz, P. Ulloa, G.
González and F. García. – 1986. Biological analysis and stock
intrusion and mix could indicate significant assessment of the giant squid Dosidicus gigas in the Gulf of
migration movements from the central and north California, Mexico during 1980. Ciencia Pesquera, 5: 63-76.
Guerra, A. and F. Rocha. – 1994. The life history of Loligo vulgaris
Pacific to the Peruvian coasts, probably induced and Loligo forbesi (Cephalopoda: Lolignidae) in Galician
by climate changes during the 1991-92 ENSO (El waters (NW Spain). Fish. Res., 21: 43-69.
Harman, R.F., R.E Young, K.M. Mangold, T. Suzuki and R.F.
Niño-Southern Oscillation). These severe, short - Hixon. – 1989. Evidence of multiple spawning in the tropical
medium term events are probably associated with oceanic squid Sthenoteuthis oualaniensis (Teuthoidea:
Ommastrephidae). Mar. Biol., 101: 513-519.
D. gigas coastal approaching and aggregations JAMARC – 1991. Joint survey report on Jumbo flying squid con-
(Ehrhardt, 1991). ducted by IMARPE and Japan Marine Resources Research
Center (JAMARC) by Shinko Maru #2 (In the waters Peruvian
Whether these groups are genetically distinct is 200 mile zone, including adjacent waters, Nov. Dec. 1989).
impossible to answer at present, but it is the neces- Tokyo. JAMARC 18: 1-58.
MIPE – 1982. Anuarios Estadísticos del Ministerio de Pesquería.
sary next step to be taken in the Dosidicus gigas Ministerio de Pesquería del Perú. Lima.
studies. In the same way, the study of age using the Nesis, K.N. – 1970. Biology of the Peru-Chilean giant squid,
Dosidicus gigas. Okeanology, 10:140-152.
statolith daily ring reading is necessary to determine Nesis, K.N. – 1983. Dosidicus gigas. In: P.R. Boyle (ed.),
if the distinctions in the growth patterns are actually Cephalopod life cycles, pp 215-231. Academic Press, London.
Nesis, K.N. – 1993. Population structure of oceanic
based on a difference in age or correspond to faster Ommastrephids, with particular reference to Sthenoteuthis
growing individuals influenced by the oceanic con- oualaniensis: A Review. In: T. Okutani, R.K. O’Dor, and T.
Kubodera, (eds.), Recent Advances in Cephalopod Fisheries
ditions. Biology, pp 375-383. Tokai University Press, Tokai.
Deeper analyses are necessary for the size at Nigmatullin, C.M. and V.V. Laptikhovsky. – 1994. Reproductive
strategies in the squids of the family Ommastrephidae
first maturity estimations in order to identify (Preliminary report). Ruthenica, 4(1):79-82.
changes in the size at first maturity during the Rocha, F., A.F. González, M. Rasero, A. Guerra, B.G. Castro and T.
Cortez. – 1996. An overview on the reproductive strategies in
periods of possible climatic influence and to Cephalopoda. ICES Working Group on Cephalopod Fisheries
obtain more evidence of the intrusion of other and Life History. Abstract. (April 1996, Lisbon, Portugal)
Rubio, J. and C. Salazar. – 1992. Prospección pesquera del calamar
populations of D. gigas. The cumulative percent- gigante (Dosidicus gigas) a bordo del buque Japonés Shinko
ages presented in figures 1 and 2 are based on Maru #2. Inf. Inst. Mar del Perú, 103: 3-32.
Soeda, J., Araya, H., Otsuki, T., Ishii, T. and Morooka, M. – 1959.
subsamples obtained during the period of study Investigations on squid resources. II. Survey Report Marine
(1991-1994). Resources in Hokkaido Region, 15: 1-106.
REPRODUCTION OF DOSIDICUS GIGAS OFF PERUVIAN COASTS 37You can also read
