Population Dynamics and Fisheries of Squat Lobsters, Family Galatheidae, in Chile
N. Bahamonde
Unlversidad de Child, Facuitad de Cienclas, Departamento de Cienolaa Ecologlpas, Casilla 653, Santiago, Chile
G. Henrfquez
Institute de Fomento Pesquero, IFOR, Divisidn de Recursos, Casilla 1287, Santiago, Chile
A. Zuleta
Subsecreiarfa de Pesea, Mlnisterlo de Economfa, Fomento y Reconstruccidn, Teatinos 120, Santiago, Chile
and H. Bustos and R. Bahamonde
Instituto de Fomento Pesquero, IFOP, Division de Recursos, Casilla 128?, Santiago, Chile
RAHAMONOE, N., C. HkNRlQUCZ, A. ZULETA, H. BUSTOS, AND K. BAHAMONDE. 1966. Population dynamics and fisheries of squat lobsters, family Galatheidae, in Child, p. 254-268. In G. S. Jamieson and N. Bourne fed.] North Pacific Workshop on stock assessment and management of invertebrates. Can. Spec. Publ. Fish. Aquat. Sci.92.
Two species of squat lobsters, Cerv/mumdct johni. Porter, and Pleuroncodes monodon, Milne Edwards, family Galatheidae. are harvested commercially off Chile. A commercial fishery began by exploiting the first spe cies bur. has gradually shifted to harvesting the second. The fishery for Pleuroncodes began in 1966 off San Antonio {L. 33°3S"SJ but has gradually moved southward and now extends to Talcahuano (37°S). There are two possible explanations for this shift in fishing area; (1) increased fishing pressure, and (2) changes in the natural environment. Some support for the second explanation is seen by simultaneous changes observed in other species which may be due to cyclic changes in the environment. Data on the fishery has been collected from 1%b to the present from the area between Coquimbo (30°S) and Talcahuano by the Fisheries Development Institute of Chile (Instituto de Fomento Pesquero, IFOP) by monitoring the fleet at landing ports and from research surveys. From 1979 to '1963 research surveys of the fishing ground were conducted in an area from 35° to 27°S between depths of 70 to-350 m and using bottom trawls designed for catching squat lobsters. Results of studies to date have provided information on the life history of each species, including reproductive patterns, minimum size at sexual maturity and an estimation of growth rate. Oceanographic factors hypothe sized to affect Pleuroncodes population dynamics are discussed.
Deux especes de galathees [Cftfvimunlda johni, Porter et Pleuroncodes monodon, Milne Edwards, famille des galatheides) font I'objet d'une peche commercial au large clu Chili, Une peche commerciale visant tout d',abord la premiere especc s'est graduellement modifier pour porter sur la seconde. La peche des Pleuron codes a debui6 en 1906 au large dc San Antonio (33° 35' S de hit.) mais s'est par la suite deplacce vers le sud; ellfi attaint maintenant Talcahuano (37° S). Ce replacement des aires de peche peut s'expliquer de deux fagons: 1) une augmentation de la ptession de peche et 2) one modification du milieu naturel. Des modifica tions observers simulta'nement chez d'autres especes et pouvant 5Lre causees par des changements cycliques du milieu appuient, du moins en parti;, la deuxiome hypothese. Des donnees sue cette peche sont rccueillies depuis 1966 dans la region s'etendant de Coquimbo (30° S) a Talcahuano Les donnees ont ete obtenues par I'lnstitut de dtSvebppement des p6ches du Chili (institute de Fomento Pesquero, IFOP) qui effectue des controles de la flottille aux ports de debarquement de m&me quo des reteves de recherche, De tels relcves des fonds de pGche ont ete realises de 1979 a 1963 dans la region comprise entre 356 et 27° de latitude sud. lis ont ete realises a des profondeurs variant de 70 a 350 m a I'aide de chaluts de fond coucus pour la capture des galathees. Les etudes effectives ont permis d'obtenir des renseignements sur le cycle vital de chaque espece, notam- ment sur les caracteristiquos yenerales de la reproduction, la tailie minimale a maturity sexuelle et le taux de crolssance estirne. Les auteurs traitent des facteurs oceanographiques que I'on suppose avoir un effet sur la dynamiquc de la population des Pleuroncodes.
Introduction 16 species, 0 are endemic to Chilean waters but only two species, C. johni Porter and P. monodon H. Milne Galatheids are part of the anomura sea fauna off Edwards are of economic importance (Fig. 1). Munido Chile. Five genera have been described: Galatbea gregaria Fabricius1 and M. subrugosa White1 may Fabricius, Pleuroncodes Stimpson, Corvimunida Bene become economically important in the near future and diet, Munido Leach, and Munidopsis Whiteaves. Of M. montemaris Bahamonde and Lopez may have some
254 COQUIMBO OUINTCRO
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I ( Cgrvimunido iohni )
Fic. 1. Annual landings of Pfouroncodes monodon and Cfiwimunida johni by port, and total national landings in Chile (1960-02). importance in the distant future. The remaining species a more restricted distribution and occurs between in Chilean waters are only of scientific interest. Coquimbo and Isla Mocha at depths between P. monodon is distributed from Lobos dc Afuera in 200-400 rn. Peru to the Bay of Ancud in Chile (Haig 1955) and The Chilean squat lobster fishery began in 1953 on occurs in depths between 20-40 m off Antofagasta C johni and In the last three decades, there have been (Gutierrez and Zuniga 1977) and from 200 to 400 rn off numerous studies on the biology of exploited species Valparaiso (Arana and Plzarro1970) (Fig. 2). C. johni has (C. johni: De Buen 1957; Fagetti 1959,1960; Alegria et al.
255 .....•••(•'•'..?-\ ,..,.#"v> rf^
Fie 2. Geographical distribution and main fishing areas for Pieuroncodes monodon >n Chile.
1%3; and Bahamonde 1965. P. monodon: Henrique* of which have not been published although the most and Bahamonde 1964; Arana and Pizarro 1970; Fagetti important points have been summarized. In recent and Campodonico 1971; Gutierrez and ZuRiga 1977 years, (G. Henrique*:, unpubl. data) research has focused Henrfquez 1979). In 1965 the Fisheries Development on why areas of highest abundance of P. monodon are (Instituto de Foment© Pesquero, I FOP) began biologi' located between 36° and 37°$ (this represents a rela cal and economic studies of squat lobster fisheries to tively small area at the southern extremity of its lati investigate additional exploitation of these resources tudinal range) and possible causes of the decrease in (Mistakidis and Henriquez 1966), This resulted in a num average commercial catch since 1970. ber of internal reports, mostly on P. monodon. many Initially in 1953 the squat lobster fishery was based
256 entirely on landings of C. johni made at Coquimbo, TABLE 1. Average fleet effort, catch and catch per unit of Valparaiso and San Antonio (Fig. 2). Landings peaked effort (CPUE) in Pleuroncodes monodon fisheries in Chile, at 14 365 t in 1965, and in 1966 fishing ranged from 1968-78. Coquimbo (19630"S) to Punta lloca (34°57"S) (Mistakidis and Henrlquez 1966). Subsequently landings Effort X1CP Catch of C johni declined gradually and in 1970, 3 812 t were 3 harvested (Fig. 1). Abundance of C johni gradually Years HO" BHP»-d) (t) CPUE It). decreased in the area between Coquimbo and 1968 0.576 9 961 17,29 Valparaiso but catches of P. monodon increased as the 19G9 1.032 23 277 22,56 fishing fleet moved further .south. In 1967 landings of 1970 1.257 37 670 29.97 the latter species amounted to 4 583 t, increasing to 1971 1.094 36 804 33,64 9 961 t in 1968. The best, squat lobster fishing grounds 1972 0.830 32 971 39.72 were located in an area from 29* to 35°S Where catches 1973 0.580 24 444 42.14 of 2 l-h~1 were made (Hancock and Henrlquez 1968). 1974 0.723 28 305 39.15 In 1970, 37 670 t of P. monodon were caught, and fish 1975 0.770 26 805 34,81 36.67 ing effort increased to 1 257 X103 BHP (Brake Horse 197ft 1.329 49 729 1977 1.443 33 087 22.93 Power) per fishing day (Henriquez and Aviles 1977). 1978 1.700 29 403 17,30 The decline in P. monodon landings between 1970-75 (Table 1) was due to political-economic conditions and "BHP (Brake Horse; Power) x fishing day, not to a decline in abundance of P. monodon. The fish ery concentrated on P. monodon when the industry The Fisheries Development Institute (IFOP) and the began to market a processed product in 1976, and this Catholic University of Valparaiso undertook a research accounted for peak landings of 49 729 t that year and survey In 1979 in the area between latitude 30°S an average effort increase to 1 329 000 BHP per fish (Coquimbo) and 38°20"S (Isia Mocha) at depths from ing day (Table 1). An analysis of catch and effort data SO to 500 m. The main objectives of this survey were to: provided by the industry showed that from 1970 to 1976 there was a steady increase in catch per unit, effort, but since 1977, catch has decreased while effort has con tinued to increase (Labra and Lederrnan 1980). In 1978 landings were 29 4001 and effort was SAN ANT0KIO TM.CAKUANO 1 700 000 BHP-d; 61% of the fleet was concentrated in 1 294 kmJ at Punta Achira Fig. 3 (Henriquez et al. 1980). The size of animals declined and the mean cephalothoracic length (CI.) decreased from 39 mm in 1967 to 27 mm in 1978 as the fishery moved southward (Pcnailillo 1981) (Fig. 3 and 4). Consequently in 1979 the - »«• Corporacion de Fomento de la Producion (CORFO) requested IFOP to undertake an evaluation of this resource. Low landings in 1980-82 (Fig. 1) were due to closed seasons imposed on fishing P. monodon; fishing for this species was only permitted as part, of another fishery. Landings of C. johni were minimal because of low abun dance. In 1983 fishing was permitted only for P. monodon. The main objectives of this study are to review the present state of biological knowledge of Chilean gala- Lheicl fisheries, to outline the scientific basis for manage ment of this resource in recent years and to discuss results of these management measures.
Research Survey Methods
This study is based on unpublished technical reports ae" of IFOP resulting from research sponsored by the Under Secretariat of Fisheries of the Ministry of Economy, Development Corporation. Some fisheries statistics of IFOP and the National Fisheries Service have been used.
'Williams (1973) suggested from culture studies that these two species were actually extreme forms of one species, M. Fie;. 3. Changes in fishing areas for squat lobsters in Chile urctt^ria Fabiicuu (by precedence). (1976-79). Penaillllo (1901).
257 5&N ANTONIO > MALES SAN ANTONIO - FEMALES
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B6r !07«0 ! ••OB ' 1427 -S- J577 3 ...,.,..«.^.-».^...,« .'••£. 3E -£ 1 X2L =L« tB422 .040 I BS4 i-^riin •• .t * jiats -OSB 4-,
' ' -1 JLOJL.X I I I I l I I I I I I ^ i i i i I I l l I- -i-l—I—l. i i I ill ii IS |9 33 27 31 35 39 43 47 61 II 15 19 23 27 31 35 39 43 47 51 Csphololhofaoic langlh (mm) Cepttolothoracic l«ng|h [ mm ) FIG. 4. Cephalolhoracic length of male and female I'leurancodes monodon from San Antonio and Talcahuano (1970-80). Pcffaillo (1981). (a) assess biomass of P. monodon in areas suitable for dom stratified sampling was planned in 1982-83 in areas trawling where squat lobsters were concentrated; three such (b) determine oceanographic characteristics and quan areas were delimited (Fig. 5); tify primary productivity in the area studied. Zone A; Punta Achira Two research vessels were used: the 0/1 Carlos Porter Zone 13: Cajon del Bio-Bio of I FOP, length 25.2 m, and the Tiberiades of the Zone C; External zone of the area. Catholic University of Valparaiso, length 19,5 m. A trawl net with a 30 m head rope and a 35.4 m foot Random samples, stratified by depth, were taken over rope was used for fishing squat lobsters. The height of the entire area in the above depth range (Table 2). the mouth ranged from 2.8 to 2.4 m and the wing tips. Table 3 shows the geographic and bathymetric distri as estimated by the method of Koyama (1974), had a bution of squat lobsters in Chile based on results of this mean separation of 11.25 m. Biomass was estimated by survey. Only C. johni was found in the area between the area swept method (Alverson ct al. 1964; Domain 31° and 36°S but both C. johni and P. monodon were 1972; Psreyra 1967; Edwards 1968;" and Kaimer et al. found in the area between 36° and 37°S. Further south 1975). both species virtually disappeared. Further surveys were carried out in 1980-81 using the same methods in an area extending from 35°4tt"S to 37*05"S at depths of TABLE 2. Position and depth of sampling stations off Chile 60-350 m which is the lower depth limit of P. monodon front October, 19W0 to September 1901 (Bustos et al. 1902). fishing. Surveys were repeated in 19B2,19B3, and 1984 (*)Over Itata Shelf. In order to locate areas of greatest abundance, estimate density, and assess size frequency distribution and Station Depth biomass. No. Latitude °S Longitude °W (m) Nine stations were sampled monthly for P. monodon 36°14'40" 72»52'40" 70 over a 12-mo period from October 19fl0 to September 36°10'40* 73*00'50" 100 1981 in a transect perpendicular to the coast off Punta 36°10'00" 73°02'50" 150 Achira (3o°13"$) at depths from 70 to 300 m with 20 to 36°09'00" 73*04'50" 200 25 minute tows using semiballoon type trawl nets 3G°09'40" 73°08'30" 250 36°09'4O" 73°15'40" 300 (Bustos et al. 1982). , Surveys in 1979,1980 and 1981 indicated squat lob 7* 36°0B'4O" 73°19 00" 200 Qfr 36ft08'45" 73*19'00" 180 sters were located in discrete geographic areas which Q* 36°08'45" 73°19'00'' 150 were separated by areas where there were none, Ran
258 TARLE 3. Geographic distribution and depth range of squat lobsters off Chile. Prom IFOP (1979).
Hauls
Geographic With With Depth range Cervimunida Pleurancodes Catch Density 1 i(m ) (latitude) N johni Wonodon (t) (kg-knrr )
30 - 31 °5 17 — — 51 - 150 10 — — 151 - 300 7 — —
31 - 32°S 22 2 — 51 - 150 6 — — 151 - 300 9 2 _.. 32.6 301 - 500 7 — —
32 - 33°S 0 — 553 51 - 150 — _ 151 - 300 11 2 _. 542.9 125 301 - 500 10 4 — 10.1
33 - 34°S 35 5 __ 09.6 51 - 150 24 2 — 151 - 300 7 2 — 64.9 23.7 301 - 500 4 1 — 24.7
34 - 35°5 70 6 ._ 9,6 51 - 150 15 _, — 151 - 300 22 6 ~ 9.6 1.5 301 - 500 5 — -
35 - 366S _7R A _ 2.2 51 - 150 2 0.4 151 « 300 30 1 — 1.7 301 - 500 9 1 - 0.1
36 - 37°S 96 4 40 62 12£ sub/one 36°00' - 36°30'S 40 3 21_ 50 75B 51 - 150 " 10 — 36 793 1.509 151 - 300 16 2 y 13 965 60 301 - 500 6 1 i i subzone 36c'30 ' - 37'00'S 40 _."!.. 19 11 367 51 - 150 31 — 17 11 2.36 663 151 - 300 12 1 2 131 65 301 • 500 3 — --
37 - 38°S 22 _!.. 51 - 150 9 151 - 300 8 1 61.1 301 - 500 5 - -
A 5 kg random sample was taken from the catch. (Tate and C lei land 1957) was used to compare size Cophalothoraeic length (CD was measured from the distributions in these three years. back of the eye socket for each specimen in the sam External morphology was observed to determine the ple with calipers to the nearest 0.1 mm. Animals in the sex of both P. monodon and C. johni. The male genital samples were sorted hy sex and the frequency of oviger- pore is located on the coxa of the fifth pair of walking ous female.s recorded. Hardness of the cephalothorax legs, and the first two swimmeret pleopods are devel was examined to determine the time of molting. Squat oped into copulating organs. The female genital pore lobsters were grouped into 1 mm intervals to provide is on the coxa of the third pair of cephalothorac legs. a size frequency distribution of animals in 1979,1902, The first pair of swimmeret pleopods is absent. Sexual and 1983. Kolmogorov-Smirnov'5 non-parametric lest maturity and lime of spawning of females were estab-
259 7S* Salinities in the area ranged from 34.2 to 34,6°/p0 at the bottom, with highest salinities observed at depths of 200 m or more. Oxygen concentrations ranged from 2 to 3 mL"1 in shallow water to a depth of 100 m, then decreased in deeper water to less than 1 mL~1 and reached a concentration of 0.5 ml""1 at a depth of 250 m. The distribution of isotherms, isohalines and oxygen isolines at the bottom tended to follow the isobathic contour (Fig. 6) which according to Silva and Blanco (1980) is indicative of an absence of vertical mixing. Subsurface equatorial water ranged from B0 to 470 in in depth on both cruises. A great part of the continen tal shelf and continental slope was covered by this water mass. Within this water mass, pockets of water occurred which had higher oxygen concentrations but whose volumes varied from year to year. Intermediate.-! antarctic water was detected below 470 m. In 1980 local upwelling was active in the vicin ity of the fishing ground off Punta Nugurne (Brandhorst 1963, 1971; IFOP 1979; Silva and Blanco 1960). The absence of upwelling during the Langostino II cruise was attributed to a lack of southerly winds before and during the cruise. Another important characteristic of the zone is thai near the coast there is mixing of subantarctic water with rain and river water.
ABUNDANCE AND DISTRIBUTION
TIG. 5. Spatial boundaries of annes: A (Punta Achira), Table 4 shows estimates of squat lobster biomass for B (Canon del Dio-nio), and C (External). each zone from 1982 to 1983. During this period biomass increased by 5 500 t and the area occupied increased by 724 km2. Zone A (Punta Achira) had the highest biomass in both years followed by Zones B lished from the frequency of ovjgerous females in each (Canon del Bio-Bio) and C. sample. Figures 7A-C show the spatial distribution of squat Two methods were used to determine age and growth lobster densities in 1979, 1982, and 1983. Distribution of P. monodon: in the last 2 years was similar. Spatial distribution by (a) Direct observations of size increases of animals kept size is shown in Fig. 8. in experimental aquaria under controlled light, tem perature, salinity, oxygen and feeding conditions. Hiatt's (1948) method was used to estimate growth TADLE 4. A. Total biomass (t) by zone of I'leuroncodes (Bustos et al. 1982). wonodon. (b) Statistical analysis of the length frequency distri bution of CL measurements of squat lobsters using 95% cunfidence Cassle's (1954, 1963) method. The modes were Arrja Biomass limits determined by visual observations. Zone (km>) (t) (0' Two oceanographic cruises were carried out to deter mine temperature, salinity, and oxygen conditions 1982 (IMS- &) in the fishing area, using research vessels IFOP- £CMA (Fishery Development Institute and School of A 775 36 23 204 13 986-32 422 B 143 41 Marine Science and Food), (IFOP 1979, Silva and Blanco 13 912 9 4IJ0-16 36S C 205 79 7 316 4144-10 487 1980). Total 1 124 56 44 432 33 B59-55 005 Results 1963 OCKANOCRAf'IIY A (Achira) J 036 29 27 004 20 444-33 565 From May 1 to June 1,1980 the water temperature B (Bio-Bio) 639 57 21 233 14 623-27 843 tended to be stable at depths between 100 and 200 m C (Exterior) 170 79 1 746 947- 2 545 and ranged from 10 to11°C except off Punta Nugurne Total 1 848 65 49 983 40 723-59 243 where the temperature was over 12°C at 100 m (Fig 6).
260 >"' to' so' jo' 10' Ww so' 40* **' SO' «0' 50' 10' 10' TV* 80' 40' 90^, -r-^y—i—I—i—I i—i—r—T—r—i—T"i—r- [ I i il ' H—^T—I—Ir^\—,—r-p—(«o
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he 6 Oceanographic conditions on squat lobster fishing grounds off Chile (Silva and Blanco. 1980). a. Oceanographic station (* b IWh M and bottom isotherms; c. Depth (-) and bottom isohalines; d. Depth M and bottom oxyyen isohnes.
261 r^3
FlC. 7, Density Ikg-km-1) distribution of Phuroncodes monodon from I HOP: A. May-August, 1979 B AnriM-30 1902 C.April-May, 19B3.
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Cepholothprocic length (mm) ^ 1399 mi • Jill He. 9. 5i3te distribution of males, females and ovi^rous HC. 8. Number of animals per kilogram in catches of Pieuron- females of Phuroncodes monodon. IFOP cruises-1979 1982 cades monodon (March-April 19B4), from IFOP. 19B3. Table!.
262 Figure 9 shows the size frequency distribution of the Pterygosquilla nrmata. There were no squat lobsters in total P. monodon population on the fishing ground in the stomach contents. Although both species were 1979, 1982, and 1983. In 1979. which was the last year caught in trawl nets, they may have been spatially sep of non-restricted fishing, the mean stae of the popula arated on the bottom because of different habitat tion was relatively low: 23.3 mm. It increased to preferences. 27.3 mm in 1982 and to 28.5 mm in 1903. A multimodal According to available information, P. monodon and frequency distribution became more evident in 1983 C. johni are demersal, at least in the adult stage. along with a considerable increase in the frequency of Pleuroncodes is found mostly in areas of green mud that specimens of > 30 mm CL Size frequency distribution have a high organic content which according to differed significantly (P< 0.05) between 1979 and 1983. Gallardo (1963) is probably due to the sinking of sur face diatoms. These phytoplankton bloom areas may BYCAICII SPECIES be associated with areas of upwclling that arc charac teristic of the central and northeast coast of Chile. Several other species of animals were caught inciden Gallardo et al. (1980) found Ampolisca araucana zocas tal to P. monodon and C, }ohni (Tables 5 and 6); these and crustacean eggs in the stomachs of P. monodon. are detailed more fully in IFOP documents (Trujillo Diatoms [Chaetoceros, Biddulphi, Synedra, Coscino- 1972; Pantoja et al. 1973; Yanei197tt; Uahamonde 1977, discus and Thdfassiosira), forarninifera, bacteria fila 197B; Labra and Lederman1979). Table 5 estimates the ments, organic detritus and fish scales were also found. amount of bycatch taken incidentally in hauls for P. monodon in an area from 36° to 37°S [Labra and SPAWNING AND SPAWNING SEASON Lcdcrman 1979). Table 6 shows the percent distribution of the different bycatch species by zones in the Talca* Analysis of samples showed variation existed in the huano Basin fishing area in two successive years. The percentage of ovigerous females caught on the fishing most important bycatch species was Merluccius gayl. grounds between April 6-20,1982 and April 15-May 8,. Pleuroncodes and Cervimunlda are preyed on by 1983; 8.1 % in 1982 and 24.6% in 1983. The percentage several species of fish (Table 7). In 1964 Hcnriqucz and of males was higher than females and ranged from 56 Bahamonde studied the feeding habits of Genypterus to 60%, The spawning season of P. monodon in the maculatus between San Antonio and Constitucidn in Talcahuano Basin extends from April to November. The central Chile and reported it as an important predator highest frequencies of ovigerous females were recorded on Pleurocondes. Of specimens of this species exam between June and October (Fig. 10) with percentages ined, 75% contained Pleuroncodes; this predator was exceeding 25% of the total number of females. The able to consume any size of Pleuroncodes present. The highest percentage of females in an advanced stage of main predators of squat lobsters appear to be Genyp incubation was recorded in July and November. The terus maculatus, Paralichthys mlcrops and Merluccius smallest ovigerous female size observed was 9 mm CL gayi. and by 40 mm CL, most females were ovigerous (Fig. 11). To determine whether the feeding habits of When spawning begins in April, ovigerous females are G. maculatus may have changed when squat lobster at depths between 200 and 300 m but seem to migrate populations declined (Henriquez and Bahamonde 1964), to .shallow waters (100-150 m) in July-August (Fig. 10) further sampling was undertaken in May 1981 and and 1979 (Ng. VI). results were reported by Bahamonde and Zavala (1981). The spawning season of Cervimunida begins one It was noted that Gnnyptarus was feeding mainly on month later than that of P. monodon, and occurs from
TAm.k 5. Estimates of biomass (0 of fauna caught intidfiiilallv in Pleuroncodes monodon fisheries Lat. 36°-37cS, 30-min trawling, menu volociLy. 2.2 knots.
Number of lows 10 29 15 10
A. Species 51-10u(m) 101-15CKm) 151~200(m) 201-300(rn) 30l-400(m)
Marluccius gayi 714 16167 2 562 2 264 2M Ccnypterus placodes — 43 6 Genyfittirus macufolus — 82 675 47 8.1 Cancroids crabs 82 2 105 49 139 Grenadiers — 167 1 957 . 24 640 4 677 Spider crab 207 110 I 004 1953 Kays - 113 513 1 291 Total biomass 1 003 18 532 5/I6fi 1 fi 730 0 30P IJ. Bycatch CPUt (kg km"1)
Average n 89 116 290
Main bycatch Species 9 78 55 233 (M. gayi) {M. gayi) £M guyi) (Grenadier*) TABLE 6. Distribution of species caught in survey cruises for 'squat lobsters in 1982 and 1983 off Chile expressed as a percentage of the catch by zone and total catch.
Zone A Zone B Zone C (Achira) (Bio-Bio) (Hxlnrior) Total Specie 1982 1983 1982 1963 1982 1983 1982 1983 Pleuroncodes monodon (laneostino Colorado) 67.99 76.13 93.94 B4.95 70.Q6 59.18 79.46 70.64 Corvimunida johni (langostino amarillo) 1.38 0.20 6.15 13.30 1.61 0.8 Merluccius gayi (merkua coniOn) 23.33 18.74 5.33 14.32 4.89 5.96 13.66 16.38 Hippoglossina rnucrops and Patalichthys microps (flatfishes) 060 1.76 0.01 0.25 0.43 2.37 0.39 1.21 Coelorhyncbus putagoninn (grenadiers) 1.15 0.15 4.36 7.73 1.22 0.48 Ccnypterus maculatus (congrio negro) 1.48 0.64 0.18 -" _>» _ Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 "Incidental catch •>No catch. TADLC 7. Main predators of Phuroncodcs monodon, between 25 mm CL, the same as observed for spawning females. 35 and 37°S (according Melendez 1981). The number of spawning females at 100 m was less than at 70 rn, but that they were larger. There were no oviger Prod a Lor CI. (mm) of squat ous females with a Cl >27 mm, but there were non frequency lobsters found spawning females at 31-34 mm CL. Spocift.s {%) inside stomachs The situation was slightly different during the second fortnight of November when the population was dis Ccnypteru.i maculatus 25.0 2.0 - 14.0 tributed between 100-150 m depth. There were two Paralichthys microps 24.5 5.0 - 14.0 Merluccius gayi 17.4 18 - 33 distinct size groups at 100 m; one with a mode at Protetihs yvgvlam 7.1 4 - 23 14 mm CL and another with a 2f> mm CL mode. The sec Trachurus murphyi 1.7 7.5 ond modal group contained the greatest number of Coelorhyncbus paidgoniit 0.0 7.3 ovigerous females. At 150 m, the dominant modal group was at 2G mm CL coinciding with the greatest number of ovigerous females. May to December with > 50% of observed females In December the population had a greater bathy- ovigerous from June to November, The smallest si^c of metric distribution (100-250 m); spawning had ended. spawning Ccrvimunida was 25 mm CL. In 1959 the aver age size of ovigerous females was 35 mm, larger than that found for Phuroncodcs in 1980-81. o0oooooooooooo The number of eggs produced by individual Pluurvn- codes females ranged from 3 000 to 6 000 depending on the size of the specimen. Figure 10 shows an esti mated fecundity curve for this species but no attempt IS79 ^_- I076 ^- I97I was made to determine whether this relationship varied over time. The fecundity of Cervimunlda is somewhat higher, ranging from 3 400 to 6 900 eggs, again depend ing on the size of the animal (Alegria et al. 1963). POPULATION DYNAMICS Analysis of data collected during 1900-81 enabled us to describe the depth distribution of squat lobsters throughout the year. In October the entire population was at a depth of 100 m and there were three distinct age groups with modes at 0, 25, and 32 mm CL. Oviger II.is IftrBo 2i-23 ft.ao si-ao 36-40 01.49 ous females of all sizes were present (Pig. 10). Oiphololhoroclc Ungfh (mm) During the first 2 weeks of November the population Re. 11. Fecundity of Pleuroncadcs monodon (0) and percent was at a depth between 70 and 100 m; at 70 m the mode age of size distribution of ovigerous females: 1971,1976,1979, was at 12 mm CL whereas at 100 m the mode was (ITOP), 1979. 264 AUQUST SEPTEMBER 70 m '•* ., ^ u t- "*• o 10 20 30 »0 10 » » * r 200 m to 10 0 250 m UU 10 20 SO 300 m 10 20 30 IO 20 50 >0 £0 30 Cephalotboracic »e*gth Imm) Pleuroncodes monodon: Monthly percentage and size distribution of ovfgerous females off Punta Achira (Table 2). Fic. 10. Solid bars are ovigenous females. There was a small mode between 13-14 mm at 250 m replaced by P. monodon in recent years. In the last 7 yr probably from the spawning the previous year. In Janu the fishery for this species has moved southward and ary and February, the population was clearly stratified is now in a well defined fishing area in the Talcahuano by depth between 250 and 300 m. The smallest animals Basin (Fig. 3). were located at 250 m. Both species C. johni and P. monodon feed on detri In March the population was located between 150 tus and the remains of marine organisms. They arc and 250 m. Stratification by size was obvious and the preyed upon by several species of fish, some of which average siz.c increased with increasing depth. In April are commercially important. the population was between 200 and 300 m and egg Populations of both species seem to be regulated by extrusion spawning had begun, the highest percentage both environmental factors and commercial fisheries. of ovigerous females was found at 300 m. In recent years population decreases have been No samples were obtained in May. In June stratifi attributed to fishing but there is evidence that natural cation was the reverse to that noted in April. Most of phenomena may also be important. A large part of the the ovigerous females were between 200 and 250 m. In detritus on which squat lobsters feed is produced in the July and August, the population had moved upwards photic zone of subantarctic water (Caliardo et al. 1900), to depths between 100 and 150 m and showed little Accumulation of detritus depends on upwelling which stratification by size. occurs in the vicinity of the present fishing grounds off In September the population had begun to stratify Punta Nugurne (Brandhorst 1963; Kelly and Blanco by size; the largest animals were found al 150 rn, also 1904). Also, in recent years clupeid fisheries have the location of most of the ovigerous females. increased in both the north and central southern area, Results of analysis of polymodal frequency curves including Talcahuano. Clupeids are large consumers of of cephalothoracic lengths using Cassie's method (1954, planklon, especially phy top lank ton, and this may affect 1963) are shown in Table B. Estimates of the modes the food supply for bentho-dcmersal detritus eating which were considered to be equivalent to annual year animals. classes were made on the basis of annual surveys and There are other factors related to detritus production these results are also included In Table 8. There were that merit investigation: variation in the transport of no significant differences between males and females. detritus by rivers and the dynamics of the subsurface As a result of experimentally raising P. monodon equatorial water mass that is dragged southward by the* larvae it was possible to distinguish 10 stages of zoea Cunlher Current. This water mass has a high salinity and and one stage of megalops (Bustos eL al. 1902). The low oxygen content (Brandhorst 1963; and Robles et al. young measured 6 mm CL at 6 mo and 11 mm at 12 mo. 1976) and expands over the upper slope of the continen tal shelf, This may explain the absence of demersal fish Discussion and Conclusion eries in the northern zone (Robles et al. 1976). Squat lobsters may live at the boundary of these water masses ff Between Coquimbo (30°S) and Isla Mocha (38°20 S)( and movement of Pleuroncodes populations may be C johni is endemic and is distributed practically over due to the dynamic interaction between them. the entire area on stoney-mud bottom. P. monodon has At present, there is insufficient oceanographlc data a wider but apparently more sporadic distribution and to explain many of the biological phenomenon occurs at least as far north as the Peruvian coast, inhab- observed with squat lobsters. Collection of oceano itating muddy bottom in areas of reduced current. graphlc data in conjunction with squat lobster abun The lif e cycle of both species is similar and they seem dance and distribution should have a high priority. to have alternating periods of abundance. Publications in the first half of the 19th century refer only to Acknowledgments P. monodon, and the first specimens of C. johni were found at the beginning of the present century. Towards We are indebted lo the International Development 1950, C johni was the only species of squat lobster Research Centre (I.D.K.C.) of Canada and the Food and exploited in the fishery, but it has gradually been Agriculture Organixation of the United Nations (FAO) for sup port of this work. We would especially like to thank our col leagues Ramon Bu*eta and Constantino Tapias for their TAHI.1' 0. Average size {CL) by age class of Pleuroncodcs assistance, and Brenda Burd and an anonymous reviewer for monodon calculated according to Cassie's method for their constructive comments on our manuscript. samples of Punta Achira (1900-01). Average siafi Average CL size (Cassic) References estimated from Males Females survey data modes e(y) AlEGRlA.U.,s. AVIU5S, AND N. RMIAMONOE. 1963. Ob«ervaclones 0 11.00 11.3 proliminares sobre la madurcz sexual del langostino [Car- 1 15.10 15.0 16.60 vimunida johni Porter). (Crustacea, Decapoda, Anomura. 2 20.20 191 24.70 Investigaciones. Zool. chilenas 9; 133-150. 3 27.40 24.0 29.00 AlVERSON, D. L., A. T. PKUTCR, ANO L L. RONHOLT. 1964. A 4 32.20 37.6 36,40 study of the demersal fish and fisheries of tho North 5 35.20 36.2 41.00 eastern Pacific Ocean. H. R. MacMillan lectures in Fish- 6 30.80 39.2 erles, Inst. Fish. Univ. British Columbia, Vancouver B.C. "190 p. 266 ARANA, P., AND M. PIV.AKRO. 1970. Analisis de los pramctros GUTIERREZ. )., AND O. 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