E/1
A SHRIMP EXPLORATORY SURVEY IN NORTHEASTERN AND NORTHERN BRAZIL, WITH SOME BIOLOGICAL OBSERVATIONS ON Penaeus aztecus

by

HITOSHI NOMURA¹ and JOSE FAUSTO FILHO
Estação de Biologia Marinha
Universidade Federal do Ceará
Fortaleza, Ceará, Brazil

Abstract

A shrimp survey was conducted by two otter trawlers in the coastal and offshore waters of northeastern and northern Brazil from 26 June to 6 July 1965.

Data on length and weight of the brown shrimp, Penaeus aztecus Ives, were collected and regression coefficients of: (1) carapace length (first: from the tip of the rostrum to the posterior mid-dorsal edge of the carapace) on total length; (2) carapace length (second: from the base of the eye notch to the posterior middorsal edge of the carapace) on total length; (3) total weight on total length; (4) tail weight on total length; and (5) tail weight on total weight were calculated. All correlation coefficients were found positive and significant (P<0.01). No significant difference was found in the sex ratio.

The main species of fishes, echinoderms, molluscs and crustaceans, found in the main shrimp fishing grounds (best indicator of shrimp grounds was Squilla lijdingi Holthuis), are listed, and some observations on penaeid catches are recorded.

Good concentrations of the brown shrimp, Penaeus aztecus, were found at 20 to 40 fm depth, on muddy bottom, particularly at 1° – 3° north latitude and 48° – 49° west longitude (northern Brazil), about 100 nautical miles off the coast of Pará State and 90 nautical miles off the coast of Amapá Territory.

¹ Present address: Faculdade de Filosofia, Ciências e Letras de Ribeirão Prêto, Ribeirão Prêto (S.P.), Brazil

CAMPAGNE DE PECHE EXPLORATOIRE DES CREVETTES DANS LE NORD-EST ET LE NORD DU BRESIL AVEC QUELQUES OBSERVATIONS BIOLOGIQUES SUR Penaeus aztecus

Résumé

Du 26 juin au 6 juillet 1965, deux bateaux pêchant au chalut à panneaux ont effectué une prospection dans les eaux côtières et au large des côtes nord-est et nord du Brésil.

A partir des données réunies sur la longueur et le poids de la crevette brune Penaeus aztecus Ives, on a calculé les coefficients de régression intéressant les rapports suivants : 1) longueur de la carapace (premièrement: de l'extrémité du rostre au bord postérieur mi-dorsal de la carapace) sur longueur totale; 2) longueur de la carapace (deuxièmement : à partir de la base de l'échancrure oculaire au bord postérieur mi-dorsal de la carapace) sur longueur totale; 3) poids total sur longueur totale; 4) poids de la queue sur longueur totale; 5) poids de la queue sur poids total. Tous les coefficients de corrélation se sont révélés positifs et significatifs (P<0,01). Aucune différence significative n'a été notée dans le rapport des sexes.

La communication contient une liste des principales espèces de poissons, d'échinodermes, de mollusques et de crustacés rencontrés sur les principaux terrains de pêchinoà la crevette (le meilleur indicateur de fonds à crevettes s'est révélé être Squilla lijdingi Holthuis) ainsi que quelques observations sur les prises de Penaeidés.

De bonnes concentrations de crevettes brunes, Penaeus aztecus, ont été trouvées par 20–40 brasses de profondeur, sur fond de vase, notamment dans la zone 1°–3° de latitude nord et 48° – 49° de longitude ouest (Brésil du nord), à environ 100 milles nautiques au large de la côte de l'Etat de Parà et à 90 milles nautiques au large de la côte du Territoire d'Amapà.

CAMPAÑA DE PESCA EXPLORATORIA DEL CAMARON EN EL NOR-EST Y NORTE DE BRASIL CON ALGUNAS OBSERVACIONES BIOLOGICAS SOBRE Penaeus aztecus

Extracto

Dos barcos para la pesca de arrastre con artes de puertas realizaron un estudio camaronero en aguas costeras y de altura al noreste y norte del Brasil, del 26 de junio al 6 de julio de 1965.

Se recogieron datos sobre talla y peso del camarón, Penaeus aztecus Ives, y se calcularon los coeficientes de regresión de: (1) la longitud del caparazón (primero: desde la extremidad del rostro hasta el borde posterior medio-dorsal del caparazón) respecto a la talla total; (2) longitud del caparazón (segundo: desde la base de la abertura del ojo al borde posterior medio dorsal del caparazón) respecto a la talla total; (3) peso total respecto a la talla total; (4) peso de la cola respecto a la talla total; y (5) peso de la cola respecto al peso total. Todos los coeficientes de correlación hallados fueron positivos y significativos (P<0, 01). No se observaron diferencias significativas entre machos y hembras.

Se enumeran las principales especies de peces, equinodermos, moluscos y crustáceos encontrados en los principales caladeros de camarones (el mejor indicador de bancos de camarones fue (Squilla lijdingi Holthuis), y se registran algunas observaciones sobre las capturas de Peneidos.

En fondos fangosos, a unas 20–40 brazas de profundidad, se hallaron buenas concentraciones de Penaeus aztecus, especialmente en los 1° – 3° de latitud norte y 48°-49° de longitud oeste (Brasil septentrional), a unas 100 millas naúticas de la costa del Estado de Pará y 90 millas de la costa del Territorio de Amapá.

1 INTRODUCTION

Two preliminary trawling surveys were made by an American firm based at São Luís (Maranhão, Brazil) in the coastal waters of Maranhão, at the maximum depth of 50 fm (91.4 m) (Lemos, 1956), with no success. Another shrimp and fish survey along and off the coast of northeastern and northern Brazil was made by the Japanese research vessel, TOKO-MARU, in 1956–57 (Nakamura et al., 1958). In the autumn of 1957, the U.S.A. exploratory fishing vessel, OREGON, made one cruise from Trinidad to the mouth of the Amazon River (Bullis and Thompson, 1959), and another one in 1963, from British Guiana to northeastern Brazil (Bullis, 1963).

The authors had the opportunity of making more detailed surveys aboard two commercial otter trawlers based at Fortaleza (Ceará, Brazil), for the purpose of obtaining preliminary information on the shrimp resources of coastal and offshore waters of Ceará, Piauí Maranhão and Pará States, and Amapá Territory. Data on length and weight of a species of pink shrimp,² Penaeus aztecus Ives, were collected and analyzed and the main species of fishes, echinoderms, molluscs and crustaceans, found in the main shrimp fishing grounds, were identified and listed. Some general observations were made on the Penaeid catches in the area.

² In Brazil P. aztecus is known as “camarão rosa” (pink shrimp) (Ed.)

2 GEAR AND METHODS

The two otter trawlers aboard which the authors made the observations, DONA MARIA and GABRIEL E/ URIAS, were 65 ft (19.8 m) long, and powered by Caterpillar diesel engines of 220 hp. Their maximum speed was 8 knots. Three cotton nets were used: a small try-net of 8 ft (2.4 m) long and two large nets of 42 ft (12.8 m), all three having a mean stretched mesh size of 31 mm at the cod-end. The try-net was always operated first, and based on the quantity of shrimp caught in 20 minutes' trawling, the larger nets were cast.

Trawling operations commenced on 26 June, and terminated on 6 July 1965.

The data obtained during the surveys made by the two boats are shown in Fig. 1 and Tables I and II. The try-net operations from the otter trawler, GABRIEL E. URIAS, were not recorded.

Soon after hauling the nets, one or more specimens of every species were fixed in formalin, for further identification at the laboratory. When the haul yielded less than 100 specimens of P. aztecus, the whole shrimp catch was used as a sample. In cases of larger catches, 100 specimens were picked up at random and all measured and weighed aboard.

The data collected from each shrimp specimen were the following:

1. total length in mm, from the tip of the rostrum to the posterior end of the telson, with the shrimp slightly extended on a ruler

2. carapace length in mm (a) from the tip of the rostrum to the posterior mid-dorsal edge of the carapace, and (b) from the base of the eye notch to the posterior or mid-dorsal edge of the carapace

3. sex

4. total weight to the nearest tenth of a gram

5. tail weight to the nearest tenth of a gram

Fig. 1 Approximate position of the trawl stations made by DONA MARIA and GABRIEL E. URIAS in the coastal and offshore waters of northeastern and northern Brazil.

TABLE I

Characteristics of the survey stations and catches of the otter trawler DONA MARIA

* Large nets; the rest, try-net

TABLE II

Characteristics of the survey stations and catches of the otter trawler GABRIEL E. URIAS

* Several try-net operations were not recorded
** Large nets; the rest, try-net

3 ANALYSIS OF THE DATA

3.1 Length and weight of the pink shrimp

The analyses of biometrical data are shown in Table III. Data on total length were grouped into 5 mm intervals, and total weight into 2.5 g intervals.

Regression coefficients of carapace length (first case: from the tip of the rostrum to the posterior mid-dorsal edge of the carapace) on total length were based on 270 males and 296 females. In this case, significant difference was found between sexes. The equations are:

where X is the total length and Y is the carapace length, both in mm.

Regression coefficients of carapace length (from the base of the eye notch to the posterior mid-dorsal edge of the carapace) on total length were calculated based on 52 males and 44 females. No significant difference was found between sexes, the equation being:

Y = - 12.00 + 0.32X (r = 1.00)

where X is the total length and Y the carapace length, both in mm.

Regression coefficients of total weight on total length were calculated by least squares of a logarithmic transformation, using data on 268 males and 295 females. No significant difference was found between sexes, the equation being:

log W = - 5.356 + 3.124 log L (r = 1.00)

where W is the total weight in grams and L the total length in mm (Fig. 2).

Regression coefficients of tail weight on total length were calculated by least squares of a logarithmic transformation, based on 61 males and 39 females. Significant difference was found between sexes. The equations are:

TABLE III

Data concerning the proportional measurements of length (mm) and weight (g) of the pink shrimp, Penaeus aztecus, sampled during June-July 1965, along and off the coast of northeastern and northern Brazil

(1) Used for obtaining the regression coefficients of carapace length (5) on total length
(2) Used for obtaining the regression coefficients of carapace length (6) on total length
(3) Used for obtaining the regression coefficients of total weight (7) on total length
(4) Used for obtaining the regression coefficients of carapace length (10) on total length
(5) From the tip of the rostrum to the posterior mid-dorsal edge of the carapace
(6) From the base of the eye notch to the posterior mid-dorsal edge of the carapace
(7) Used for obtaining the regression coefficients of total weight on total length (3)
(8) and (9) Used for obtaining the regression coefficients of tail weight on total weight
(10) Used for obtaining the regression coefficients of tail weight on total weight (4)

Fig. 2 Regression of total weight on total length of the pink shrimp, Penaeus aztecus.

where W is the tail weight in grams and L the total length in mm.

Regression coefficients of tail weight on total weight were calculated using data on 61 males and 39 females. Significant difference was found between sexes. The equations are:

where X is the total weight and Y the tail weight, both in grams.

3.2 Sex ratio

The total number of specimens sexed was 566, of which 270 were males (47.7 percent) and 296 females (52.3 percent). Chi-square test (X² = 1.18; P>0.05) showed that there is no significant difference in sex ratio from the expected ratio of 1:1.

3.3 Accompanying fauna

During the entire survey, 65 species of fishes were recorded in the catches. The most abundant species were: shark, Scoliodon terrae-novae Richardson; guitarfish, Rhinobatus percellens (Walbaum); rays, Gymnura micrura (Bloch and Schneider), Dasyatis gymnura (Müller) and Urotrygon microphthalmum Delsman; catfish, Felichthys bagre (Linnaeus) and Galeichthys sp.; moray eels, Ariosoma nitens? (Jordan and Bollman), Ophichthus magnioculis (Kaup), Gymnothorax ocellatus Agassiz and Gymnothorax jordani (Evermann and Marsh); goatfish, Prionotus caprella? (Ribeiro); lane snapper, Lutianus synagris (Linnaeus); grunt, Conodon nobilis (Linnaeus); soles, Scyacium latifrons? (Jordan and Gilbert), Achirus fasciatus (Lacépède), Achirus sp. and Symphurus elongatus? (Günther).

Nine species of echinoderms were recorded during the survey and of these, three, Luidia senegalensis (Lamarck), Astropecten marginatus Gray; and the brittlestar, Ophioderma sp. were the most abundant.

Twenty species of molluscs were recorded during the survey of which only one, the scallop, Amusium papyraceus Gabb, occurred in any number in the main shrimp fishing grounds.

Thirty-seven species of crustaceans were recorded of which only five were abundant, viz: the shovel-nosed lobster, Scyllarides delfosi Holthuis; crabs, Calappa nitida Holthuis, Calappa sulcata Rathbun and Callinectes danae Smith; and the mantis shrimp, Squilla lijdingi Holthuis. This last species was found to be the best indicator of shrimp grounds. Among the Penaeidae, seven species were recorded in the following order of importance: pink shrimp, Penaeus aztecus; sea bob shrimp, Xiphopenaeus kroyeri (Heller); white shrimp, Penaeus schmitti Burkenroad; Solenocera geijskesi? Holthuis; rock shrimps, Sicyonia typica (Boeck) and Sicyonia dorsalis Kingsley; and Trachypenaeus constrictus (Stimpson).

4 DISCUSSION

4.1 Penaeid catches

Young and medium-sized pink shrimp, P. aztecus, were caught in coastal waters of Maranhão and Pará States (station nos. 3, 6, 7, 9, 13, 15 and 5', 6', 10'), but not in large quantities. According to observations of Coelho (1963), this species is abundant in the catches of stop seines and trap nets in estuaries and along the beaches of Maranhão State. Large ones were caught only in offshore waters of Pará State and Amapá Territory (station nos. 17/28 and 11'/15'), at 20 to 40 fm (37 to 73 m) depth, on muddy bottom. Lemos (1956) was of the opinion that surveys should be made at 150 to 200 fm (274 to 366 m) depth because adult shrimps inhabit deep waters. No opportunity to trawl at these depths was given, but large shrimps were taken by us at 40 fm depth, off Pará State and Amapá Territory. Holthuis (1959) also states that adult specimens of pink shrimp are, as a rule, found farther offshore (12 to 30 fm (22 to 55 m) depth). In offshore waters of Maranhão State, however, the bottom at over 22 fm (40 m) depth is composed of corals, and is not suitable for trawling (Nakamura et al., 1958).

The TOKO-MARU report (Nakamura et al., 1958) recommends shrimp fishing in the coastal zone of Maranhão State. In waters south of Pará River, the above research vessel made only five trawling stations over a small flat zone, of 10 to 16 fm (18 to 29 m) depth, and it was observed that the muddy zone, north of Pará River, must be more promising fishing ground than the southern zone.

It is reported (Anon, 1953) that offshore waters from the Amazon River to Recife (Pernambuco) yield heavy catches of large shrimp from June through September, but the scientific names of the species are not given.

Lindner (1957) states that about 60 percent of the catch in the area between Marajó Bay and São Luís, and in the area around Parnaíba appear to be sea bobs, while the young of P. schmitti and of P. aztecus together constitute 40 percent. According to the same author, shrimps are caught throughout the year in northern waters. Coelho (1963) states that in the coastal waters of Maranhão State the best period of shrimp fishing is from April to August, after the rainy season.

In the neighbourhood of the area surveyed, where P. aztecus was taken (latitudes 1° to 3° N and longitudes 48° to 49°W), the exploratory fishing vessel OREGON made sporadic catches of that species in the autumn of 1957 (Bullis and Thompson, 1959). Pink shrimps were taken in depths from 10 to 50 fm (18 to 91 m), but beyond 40 fm (73 m) the quantity caught was considerably less, occurring more frequently in the 25 to 30 fm (46 to 55 m) range along with Penaeus brasiliensis Latreille. However, in our samples of shrimp catches from this region and made at 20 to 40 fm (37 to 73 m) depth, we did not find any P. brasiliensis but only P. aztecus. Both vessels as well as the OREGON found them predominantly on muddy bottoms, the best catches of the latter amounting to 30 to 45 lb (13.6 to 20.4 kg) per h (heads-on).

During the present survey, 28 boats were sighted operating in the area, confirming the statement of Richardson (1962) that foreign-based shrimp boats were fishing off the mouth of the Amazon River. One of the 28 boats, GULF KING III, from Barbados, caught an average of 1,000 lb (454 kg) (heads-off) per night's fishing (12 h), equivalent to about 83 lb (37.6 kg) (heads-off) per h, much more than recorded by OREGON. Our vessel, DONA MARIA, caught only about 280 lb (127 kg) (heads-off) from sundown of 4 July to dawn of 5 July 1965 (12 h), equivalent to about 23.3 lb (10.6 kg) (heads-off) per h. We noticed that the fishermen of our boats were not so skilled as the ones from Barbados.

As to the white shrimp, P. schmitti, only six large specimens were caught at 3 to 7 fm (5.5 to 12.8 m) depth, in the coastal waters of Maranhão State (station nos. 4, 11, 13 and 9'), alone or mixed with medium-sized pink shrimp, P. aztecus.

Large-sized specimens of white shrimp are commonly caught in estuaries and beaches of Maranhão coast (Coelho, 1963), but due to the few stations made in the present survey, it is not possible to state whether white shrimp is, or not, abundant in offshore waters.

Small quantities of sea bob were caught at station nos. 14, 15, 10' (inshore waters of Maranhão and Pará States), and 11' (offshore waters of Pará State).

One specimen of Sicyonia typica was found at station no. 26, and three of Solenocera geijskesi? at station no. 13', both mixed with P. aztecus; one specimen of Sicyonia dorsalis, and one specimen of Trachypenaeus constrictus, at station no. 10', both mixed with P. aztecus, schmitti and X. kroyeri.

4.2 Proportional measurements of the pink shrimp

Correlation coefficients of all the measurements studied are positive and significant (P<0.01). Of the regression coefficients of carapace length on total length, the second one, where carapace length is measured from the base of the eye notch to the posterior mid-dorsal edge of the carapace, showed no significant difference between sexes, while the first, where carapace length is measured from the tip of the rostrum to the posterior mid-dorsal edge of the carapace, presented significant difference.

These proportional measurements being closely correlated, it is possible to designate sizes by carapace length (from base of eye notch to posterior mid-dorsal edge of carapace) and convert it easily into total length, total weight and tail weight, by making use of those regression coefficients.

5 CONCLUSIONS

The main purpose of the survey was to obtain information on the shrimp resources of northeastern and northern Brazil. In northern Brazil good concentrations of the pink shrimp were found in July 1965 at 20 to 40 fm (37 to 73 m) depth, on muddy bottom, particularly at latitudes 1° to 3°N and longitudes 48° to 49°W, about 100 nautical miles off the coast of Pará State and 90 nautical miles off the coast of Amapá Territory. In northeastern Brazil the offshore waters are not rich in shrimp resources, at any rate in the area surveyed.

The best indicator of shrimp grounds was found to be mantis shrimp, Squilla lijdingi.

6 REFERENCES

Bullis, H.R., Jr., 1963 R/V OREGON Cruise Report No. 84. Pascagoula, U.S. Department of the Interior, 4 p

Bullis, H.R., Jr., and J.R. Thompson, 1959 Shrimp exploration by the M/V OREGON along the northeast coast of South America. Comm Fish.Rev., 21(11): 1–9

Coelho, R.R., 1963 Aspectos bio-tecnológicos de pesca marinha no Maranhão, Piauí e Ceará. Bol.Estud.Pesca, Recife, 3(6):8–18

Holthuis, L.B., 1959 The Crustacea Decapoda of Suriname (Dutch Guiana). Zool.Verh.Leiden, (44):296 p

Lemos, J., 1956 Relatório da missão portuguesa de pesca no Brasil. l. Introdução ao estudo das pescas no Brasil. Lisboa, 326 p.

Lindner, M.J., 1957 Survey of shrimp fisheries of Central and South America. Spec.scient Rep.U.S.Fish Wildl.Serv., (235):166 p.

Nakamura, H., et al., 1958 Survey report on the Brazilian fishing grounds by the TOKO MARU (translated from Japanese). Tokyo, Tokyo Fishery University. 388 p (Mimeo)

Richardson, I.D., 1962 Survey of Brazilian fishing grounds. Fishg News Int., 1(4):42–4

Anon., 1953 Brazil: shrimp fishery expansion possible. Comm Fish.Rev., 15(12):36