REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016) 37

REVISIÓN

BIOLOGY AND FISHERY OF THE SOUTHERN ( australis) IN THE SOUTHWEST ATLANTIC OCEAN*

ANALÍA R. GIUSSI1, FEDERICO L. GORINI, EMILIANO J. DI MARCO, ANABELA ZAVATTERI and NOEMÍ R. MARÍ Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo N° 1, Escollera Norte, B7602HSA - Mar del Plata, Argentina 1e-mail: [email protected]

SUMMARY. Southern hake (Merluccius australis) is distributed mainly south of 50° S around South America, occurring in cold temperate waters of subantarctic origin. In the Southwest Atlantic Ocean (SAO) only adults are abun- dant. This species is icththyophagous and malacophagous, feeding mainly on long tail hake (Macruronus magellanicus) and several (Illex argentinus, Onykia ingens, gahi). Age and growth studies show significant sexual differences; females grow to a larger size than males. In recent years, the highest biomasses, estimated from trawl surveys using the swept area method, are about 10,000 t. Fish 4 to 8 years old usually dominate commercial land- ings. Only a few factory trawler vessels have southern hake as a target species. They operate over the main fishing grounds located near Tierra del Fuego and at the eastern mouth of the Beagle Channel. Average annual landings are about 5,000 t.

Key words: Merluccius australis, Southern hake, SAO, biology, catches, fishery.

BIOLOGÍA Y PESQUERÍA DE LA MERLUZA AUSTRAL (Merluccius australis) EN EL OCÉANO ATLÁNTICO SUDOCCIDENTAL

RESUMEN. La merluza austral (Merluccius australis) se distribuye principalmente al sur de los 50° S alrededor de América del Sur, encontrándose en aguas templado-frías de origen subantártico. En el Océano Atlántico Sudoccidental (OAS), solo los adultos son abundantes. Esta especie es ictiófaga y malacófaga, y se alimenta principalmente de la mer- luza de cola (Macruronus magellanicus) y de varias especies de cefalópodos (Illex argentinus, Onykia ingens, Doryteuthis gahi). Los estudios de edad y crecimiento indican la presencia de diferencias significativas entre sexos, siendo las hembras mayores que los machos. En los últimos años, las biomasas más altas estimadas por el método de área barrida, se encontraron alrededor de las 10.000 t. Las capturas se encuentran principalmente integradas por indi- viduos de 4 a 8 años de edad y solo unos pocos buques factoría arrastreros capturan a la merluza austral como especie objetivo. Dichos buques operan en los principales caladeros, próximos a Tierra del Fuego y a la entrada este del Canal Beagle. Los desembarques promedios anuales se encuentran cercanos a las 5.000 t.

Palabras clave: Merluccius australis, merluza austral, OAS, biología, capturas, pesquería.

*INIDEP contribution no. 2027 38 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

Norman (1937) compared individuals from both INTRODUCTION areas and concluded that they were the same species, giving it its present designation, M. aus- tralis. Some authors (Ciechomski and Weiss, Representatives of Genus Merluccius are high- 1974; Cousseau and Cotrina, 1981) referred to the ly abundant in the Southwest Atlantic Ocean species as M. polylepis, which at present is con- (SAO). The two occurring species, M. australis sidered an obsolete designation. and M. hubbsi, show remarkable morphological similarities, making their identification difficult in areas where they occur together. While the dis- PHYSICAL ENVIRONMENT tribution areas of the two species are contiguous, in the absence of oceanographic barriers, their separation is likely related to a combination of The water circulation over the Patagonian shelf factors such as food availability and physiologi- region (Figure 1) depends on various factors such cal adaptability to different water masses (Giussi as local winds, tide wave propagation, fresh water et al., 2005). discharge and the influence of the deep currents In the Argentine Sea, the Southern hake (M. (Guerrero and Piola, 1997, Sabatini et al., 2004). australis) more abundant schools are present The water mass of the Patagonian shelf is from 52° S southwards. Population structure data influenced by the Antarctic Circumpolar Current suggests that these individuals could be related to which gives special characteristics to the region. the main stock that inhabits in the Pacific Ocean After reaching the Drake Passage it divides into (Aguayo-Hernández, 1995; Bezzi et al., 1995). two principal branches. One branch flows Probably this species could be endemic to Pacific between Tierra del Fuego and Isla de los Estados waters that colonized the SAO region in recent through the Le Maire Strait, and it is known as the geologic times (Cousseau, 1993). It is likely that Cape Horn Current (Hart, 1946; Boltovskoy, the ability of the species to disperse from the 1970). The other branch is the Malvinas Current, Pacific Ocean was somehow restricted at some which divides into an eastern and western branch point, and later it occupied an ecological niche in when it reaches the Burdwood Bank. While the the Atlantic that was suitable to its requirements. waters of the western branch are diluted signifi- Competition with other species and the absence cantly by continental runoff and ice melting of appropriate spawning and nursery grounds (Lusquiños and Valdés, 1971; Piola and Gordon, may have also limited its expansion (Aguayo- 1989; Piola and Rivas, 1997; Guerrero et al., Hernández, 1995; Giussi et al., 2005). 1999), the eastern waters are denser and move northward along the border of the continental slope, showing higher salinity and lower average temperature. The other water mass called the Patagonian Current flows northward along the coast. This M. australis has several synonyms (Cousseau, includes the contribution from continental rivers 1993). Hutton (1872) was the first to describe the and also diluted water from the Strait of species from samples collected in New Zealand Magellan. Local precipitation in the Southwest waters naming it Gadus australis. Günther (1887) Pacific (with annual means greater than 5,000 classified individuals from the Strait of Magellan mm) and the seasonal melting of glaciers reduce into the current genus under the name M. gayi. salinity in this region (Sabatini et al., 2004). GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 39

S

50 m 100 m 45°

San Jorge Gulf

47°

Argentina

Current

49° Malvinas 1 ,000 m

200 m Patagonian Current

Malvinas Islands 51°

Strait of Magellan hannel 53° Malvinas C 200 m 200 m Burwood Bank Figure 2. The geographical distribution of Merluccius aus- tralis around Southern South America. 55° 1, 000 m Figura 2. Área de distribución geográfica de Merluccius Cape Horn Current australis en el extremo sur de América del Sur. W6°86°66°46°2 60° 58° 56 ° Figure 1. General scheme of the water masses and current (1982) have reported lower latitudes for the circulation on the Patagonian shelf. Taken and modi- northernmost limit of its distribution. However, fied from Sabatini et al. (2004). because the species was only sporadically report- Figura 1. Esquema general de las masas de agua y circula- ed from these northern latitudes, it is likely that ción de las corrientes marinas en la plataforma patagónica. Tomado y modificado de Sabatini et al. large-sized individuals of its congener M. hubbsi (2004). might have been misidentified. Its vertical distribution is related to its demer- sal habits, and thus it is found near the seabed in GEOGRAPHIC DISTRIBUTION depths from 100 m to > 1,000 m in cold waters of the Malvinas Current (Otero and Simonazzi, 1980), mainly at low temperature (3 to 9.5 °C) Like other merluccid hake, Southern hake has and high salinities (32.8 to 34.18) depending on a wide distribution. It occurs in both the Atlantic the season (Wöhler, 1987; García de la Rosa et and Pacific Oceans surrounding the southern tip al., 1997; Giussi et al., 2005). of South America, and it is also present in New Relatively high densities have been found in Zealand waters (Aguayo-Hernández, 1995; Bezzi waters at 52° S and > 150 m depth, with salinity et al., 1995; Horn, 2015). In the Atlantic Ocean ranging 33.5-33.8 and temperature values close to (Figure 2) it is distributed south of 50° S down to 8 °C (Figure 3). However, it also occurs frequent- the Cape Horn (56° S), extending into the Pacific ly in slope waters at 34.0 salinity and 6 °C aver- Ocean through the Drake Passage (García de la age temperature. Waters of the Patagonian Rosa et al., 1997). Cotrina (1981) and Otero et al. Current and those related to the continental slope 40 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

14

12

10

8

6

4

Temperature (°C)

2

0 32.5 32.8 33.0 33.3 33.5 33.8 34.0 34.3 34.5 Salinity

Figure 3. Density (t nm-2) of Merluccius australis in relation to both bottom temperature and salinity. Redrawn from Giussi et al. (2005). Figura 3. Densidad (t nm-2) de Merluccius australis en relación con la temperatura y la salinidad de fondo. Redibujado de Giussi et al. (2005). are both suitable habitats for the southern hake in resin and transversally cut with a diamond- from their perspective of salinity and tempera- tipped saw. This method enables more precise ture, but they are sporadically visited by the sectioning through the nucleus, resulting in less species, probably related to the availability of bias in counts and the best definition of the mar- preys (Marí and Sánchez, 2002; Sánchez and ginal increments (Figure 5). The maximum ages Marí, 2005; Giussi et al., 2005). recorded for males and females were 14 and 18 years, respectively, while the minimum was 3 years old (Gorini et al., 2010). BIOLOGY AND LIFE HISTORY The growth in length of the Southern hake has been adequately fitted using the von Bertalanffy (1938) model, and revealed differences between Age and growth sexes (Gorini et al., 2010). Males have a growth rate parameter (K) notably higher than females, Age is derived from counts of zones in the although their asymptotic length (L∞) is lower: sagittae otoliths. These otoliths are thin and oblong, with a prominent rostrum and toothed Males TL = 82.05 cm (1− e − 0.277 (t − 0.9929)) edges on the dorsal and ventral borders. In the ventral zone there is a longitudinal depression Females TL = 100.19 cm (1− e − 0.137 (t + 1.137)) flanked by an inferior and a superior crest, which extends parallel to the main axis of the structure; Length-weight relationship this is called the sulcus acusticus (Figure 4). Otoliths are processed using standard tech- The relationship between total length and niques widely used for merluccids and other weight was estimated as: species (Christensen, 1964), although slightly modified by Gorini et al. (2010). Otoliths are first W = 0.0029 * TL3.2007 R2 = 0.9478 baked to enhance growth zones, then embedded GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 41

Due to the incomplete population structure of Ventral edge southern hake in the SAO, data from several years were used to fit this equation. But first, lin- ear regressions between length and weight were estimated for each year, and their slopes were compared by multiple Tukey-Kramer tests (Zar, 1999). There were no statistically significant between-year differences, thus allowing the esti- Striaes mation of a single equation. Dorsal edge Postrostrum Rostrum Crista superior Natural mortality Ostium Cauda Instantaneous rate of natural mortality (M) was estimated using different equations that consider growth parameters as well as abiotic variables (Pauly, 1980; Jensen, 1996). The M values for Crista inferior both sexes pooled were 0.19 and 0.18 year-1, depending on the methodology applied: Sulcus Figure 4. Sagitta otolith of Merluccius australis. - Pauly (1980): Figura 4. Otolito sagitta de Merluccius australis.

logM = − 0.0066 – 0.279 log 102.03 + (Micromesistius australis, 18% frequency), other 0.6543 log 0.12 + 0.4634 log 9 fishes are also ingested sporadically depending on their seasonal availability in the area. - Jensen (1996): Cephalopods such as Illex argentinus, Doryteuthis gahi, Onykia ingens and Eledone sp. M = 1.5*0.12 (6-12% frequency) are secondary prey, while macrocrustaceans such as Austropandalus grayi These values were similar to the ones compiled and Eufausia lucens (Marí and Sánchez, 2002; by Horn (2015), for the New Zealand stock and Sánchez and Marí, 2005) and the salp, Ihlea mag- those obtained by Quiroz et al. (2014) for the alhanica (Thaliaceae), are occasional items in the Chilean stock. diet. Both sexes have a similar diet (Table 1; Figure 6). Feeding Parasitism M. australis is part of the demersal community acting as a macrophagous predator (Angelescu Both myxosporids and cestodes parasitize and Prenski, 1987). Being primary ichthyofagous Southern hake in the Atlantic Ocean. Among the and secondarily malacophagous, its trophic level former, Alatospora merluccii n. sp. and Myxidium is 4.50 (Wöhler et al., 1999; Marí and Sánchez, baueri Kovaleva and Gaevskaya 1982 have been 2002; Sánchez and Marí, 2005). Although the found in the gall bladders (Kalavati et al., 1995), most important food items are gadiform species, while the cestode Clestobothrium splendidum sp. especially long tail hake (Macruronus magellani- n. (Gil de Pertierra et al., 2011) has been found in cus, 55% frequency) and the intestine. 42 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

A

B

C

Figure 5. Merluccius australis otolith transverse sections, observed with stereoscopic microscopic at 10X magnification, sho- wing the translucent zones. A) 44 cm total length (TL), 3 zones. B) 69 cm TL, 8 zones. C) 83 cm TL, 14 zones. Taken and modified from Gorini et al. (2010). Figura 5. Secciones transversales del otolito de Merluccius australis, observadas con microscopio estereoscópico y un aumento de 10X. Se identifican los anillos hialinos. A) 44 cm de longitud total (LT), 3 anillos. B) 69 cm LT, 8 anillos. C) 83 cm LT, 14 anillos. Tomado y modificado de Gorini et al. (2010).

Table 1. Food items found in stomach contents of Merluccius australis. Tabla 1. Ítems presa encontrados en los contenidos estomacales de Merluccius australis.

Phylum Class Family Species/genus Common name

Vertebrata Osteichthyes Macruridae Macruronus magellanicus Long tail hake Gadidae Micromesistius australis Southern blue whiting Notothenidae Patagonotothen ramsayi Nototheniids Moridae Salilota australis Red cod Merluccius hubbsi Argentine hake Cephalopoda Ommastrephidae Illex argentinus Argentine shortfin Dorytheutis gahi Patagonian squid Onychoteuthidae Onykia ingens Greater hooked squid Eledonidae Eledone sp. Musky octopus Crustacea Malacostraca Pandalidae Austropandalus grayi Eufausiidae Eufausia lucens Krill Tunicata Thaliacea Salpidae Ihlea magalhanica Salps GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 43

Fishes

Cephalopoda

Crustaceans

0 10 20 30 40 50 60 70 80 90 100 F% Figure 6. Merluccius australis trophic spectrum (%F) in the Southwest Atlantic Ocean. Figura 6. Espectro trófico (%F) de Merluccius australis en el Océano Atlántico Sudoccidental.

Reproduction The length at sexual maturity (TL50%) estimat- ed for the two sexes combined is 59.5 cm total There is little information about the southern length (TL) (Figure 8), corresponding to an age of hake reproductive biology in the Southwest 4.5 years old (Gorini et al., 2012). These estimates Atlantic. This is mainly due to the relatively low were obtained from the macroscopic observation abundance of this species in this region −particu- of the gonads, using the same 5 stages maturity larly of juveniles−, and the lack of evidence for a scale as applied in reproductive studies of M. well-defined spawning season and area. hubbsi (Macchi and Pájaro, 2003). When ovaries Some histological studies suggest that spawn- become opaque and show evidence of spawning ing may occur between July and September over but with many yolked oocytes (from stage 2 the continental shelf (Cotrina, 1981). However, onward) individuals were considered mature. Ciechomski et al. (1975), using postlarvae length and histological methods, concluded that spawn- ing would take place between October and FISHERY November near the Malvinas Islands. Ciechomski and Weiss (1974) described the larvae and postlarvae of the species from speci- Yields and abundance estimates mens caught over the shelf off Tierra del Fuego and the southwestern coast of the Malvinas An abundance index for the Southern hake in Islands. These authors emphasized the morpho- the Southwestern Atlantic was obtained directly logical similarity observed with its congener M. from trawl surveys using the swept area method hubbsi in many aspects. Differences between the (Alverson and Pereyra, 1969) during the Instituto two species were found in the pigmentation, body Nacional de Investigación y Desarrollo Pesquero proportions, ossification rate, and formation of (INIDEP) annual assessment cruises in the region the caudal fin (Figure 7). (Wöhler et al., 1999), carried out in summertime 44 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

A from 1992 to 2009. These estimates may be biased however, because of the surveys cover only a part of the total distribution area (Figure 9), and do not include the higher latitudes where the largest fish- 1 mm ing yields are obtained. In view of these difficul- ties, the catches per unit effort (CPUE) were used to produce an alternative series of relative abun- B dance indices. Both abundance series showed a clear tendency of decreasing biomass through the period 1997-2010, although some variability was observed, particularly from 1997 to 2001. The trend shown by the CPUE index was similar to the 1 mm one obtained from data collected during the assessment surveys (Figure 10). The stock assessment was performed using a C statistical catch-at-age model (Giussi and Zavatteri, 2016) implemented in the AD Model Builder platform (Fournier et al., 2012). The model was tuned with the annual catch data, 1 mm catch-at-age compositions and the abundance index (CPUE) derived using data obtained from the commercial fleet in the period 1992-2015. The assessment comprised 30 years, from 1986 to D 2015 and two models were evaluated considering two different values of M due to the stock dynam- ic of Southern hake in SAO is not completely understood. Both models denoted spawning stock is currently over 30% SB0, considering SB0 as the 1 mm first year of diagnosis (1986) nearly to the unfished status. A strong decrease in abundance was observed at the beginning of the period, E probably related to the fishing pressure over the stock (Figure 11). Although a similar trend was observed in the stock distributed in the Pacific Ocean (Quiroz et al., 2013), the absolute abundance of the SAO 1 mm stock was estimated to be only arround one-tenth of the Pacific stock (Giussi et al., 2016). Figure 7. Merluccius australis postlarvae pigmentation. A) 4 mm. B) 6 mm. C) 10 mm. D) 17 mm. E) 25 mm. Taken and modified from Ciechomski and Weiss Commercial catches (1974). Figura 7. Pigmentación de las postlarvas de Merluccius aus- Historically, commercial catches of M. aus- tralis. A) 4 mm; B) 6 mm; C) 10 mm; D) 17 mm; E) 25 mm. Tomado y modificado de Ciechomski y Weiss tralis have been low in comparison to other fin- (1974). fish species occurring in the same area. Because GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 45

1.00 A

0.75

0.50

Proportion 0.25

0.00 36 41 46 51 56 61 66 71 76 81 87 93 Total lengt h (cm)

1.00 B 0.75

0.50

Proportion 0.25

0.00 12345678910111213 Age (years)

Figure 8. Proportion of mature Merluccius australis in relation to total length (A) and age (B). Figura 8. Proporción de individuos maduros de Merluccius australis, en relación a la longitud total (A) y a la edad (B).

S Relative abundance -2 (t nm ) 48° 0.1 11.6

50°

52°

54°

W 70° 68° 66° 64° 62° Figure 9. Relative concentrations of Merluccius australis estimated during summer cruises. Figura 9. Concentraciones relativas de Merluccius australis estimadas durante los cruceros de verano. 46 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

0.14

0.12

0.10

-1 0.08

0.06

CPUE (t h )

0.04

0.02

0.00

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Year Figure 10. Catch per unit effort (CPUE) from the Argentine fleet. Period 1992-2015. Figura 10. Captura por Unidad de Esfuerzo (CPUE) de la flota argentina. Período 1992-2015.

150,000

120,000

90 ,000

SSB (t) 60 ,000

30 ,000

0 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 Year M: 0.33 M: 0.21 Figure 11. Estimated stock spawning biomass (SSB) trajectory as a result of the stock assessment, during the period 1986-2015, considering two natural mortality values. Figura 11. Evolución de la biomasa desovante (SSB) como resultado de la evaluación de abundancia correspondiente al período 1986-2015, considerando dos valores de mortalidad natural. GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 47 of this relatively low abundance (Marí and between 700 and 800 m depth (Figure 14). Giussi, 2003), Southern hake is primarily a Captures and yields show a similar tendency when bycatch of the long tail hake fishery, which is the they are analyzed monthly (Figure 15). Lowest major target species within the main fishing values of both are recorded between June and grounds in the region (Gorini et al., 2014). October. At this time of the year, M. australis The species is caught south of 47° S, the main occurs in low numbers in Argentine waters, proba- fishing grounds being located between 54° S and bly because a large proportion of the population is 55° S (Figures 12 and 13), where relatively higher in Chilean waters for spawning during winter yields are obtained between 200 and 400 m and (Aguayo and Zuleta, 1988; Aguayo-Hernández, 1995). Catches increase later in summer, likely S because of the larger availability of long tail hake Average catches (t) schools, which is the main prey of Southern hake 0.057 49° (Wöhler et al., 1999; Marí and Sánchez, 2002; 41.11 Giussi et al., 2004; Sánchez and Marí, 2005).

51° Annual migration of Southern hake between the Southeast Pacific Ocean and SAO appears likely.

53° Total length in commercial catches

55° From the four years where data are available, the length frequency distribution of M. australis 57° caught by the Argentine fleet is unimodal W 73° 70° 67° 64° 61° 58° 55° (Figure 16) with the peak around 60-70 cm total Figure 12. Merluccius australis fishing grounds in the Southwest Atlantic Ocean, indicated by locations of length (TL). Maximum length is slightly larger catches summed into 1° squares of latitude/longitude than 100 cm TL while average values are about over the years 2006 to 2012. 68 cm TL. Catches comprise mainly adults with Figura 12. Caladeros de Merluccius australis en el Océano a small proportion of juveniles (≤ 15%), Atlántico Sudoccidental por rectángulo estadístico de 1º de latitud y 1° de longitud, entre los años 2006 although with some inter-annual variability. Sex y 2012. ratio is close to 1:1.

0.6 70

0.5 60 50

-1 0.4 40 0.3 30

Percentage

CPUE (t h0.2 ) 20 0.1 10 0.0 0 50 51 52 53 54 55 56 Latitude (°S) Yield Catch Figure 13. Merluccius australis average yield (CPUE) and catch obtained by latitude. Period 1997-2010. Figura 13. Rendimiento promedio (CPUE) y captura de Merluccius australis, en relación con la latitud. Período 1997-2010. 48 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

0.35 0.30 0.25

-1 0.20 0.15

CPUE (t h0.10 ) 0.05 0.00

<100

> 1,000

100-199

200-299

300-399

400-499

500-599

600-699

700-799

800-899

900-999 Depth (m) Figure 14. Merluccius australis average yield (CPUE) in relation to depth. Period 1997-2010. Figura 14. Rendimiento promedio (CPUE) de Merluccius australis en relación con la profundidad. Período 1997-2010.

20 0.5

0.4 15

-1 0.3 10 0.2

Catch (%)

CPUE (t h ) 5 0.1

0 0.0 Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec. Month Figure 15. Merluccius australis average yield (CPUE) and catch per month. Period 1997-2010. Figura 15. Rendimiento promedio (CPUE) y captura de Merluccius australis obtenidos por mes. Período 1997-2010.

Catch at age presence of foreign fleets operating in areas close to the Argentine Exclusive Economic Zone The age structure of commercial catches obtained (AEEZ) (Gorini et al., 2007). In those years the by scientific observers on board of commercial fleet catches exceeded 9,000 t, thereafter decreasing has been variable through time (Figure 17) and thus markedly down to 3,000-7,000 t. In recent years annual classes or cohorts are difficult to follow. (2006-2015), annual catches averaged 5,300 t Juveniles are scarce and individuals 4 to 8 years old (Giussi and Zavatteri, 2016). are the most abundant (Gorini et al., 2012). The fishing fleets currently catching M. australis in the SAO include large vessels with enough Landings and commercial aspects autonomy to remain for a long period of time in the fishing grounds. These vessels are trawlers that use Relatively larger landings occurred through the bottom or mid-water nets. Catches are processed period 1987-1990 (Figure 18) mostly due to the on board and fish is maintained at temperatures GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 49

7,00

6,00

5,00

4,00

3,00

eg P rcenta e 2009 2,00 2008 2007 1,00 2006 2005 0,00

41 61 81

33 53 73 93

25 45 65 85

37 57 77 97

29 49 69 89

101

113

105 T(cm)L 109 Figure 16. Percentage of total length (TL) in commercial catches of Merluccius australis in the Southwest Atlantic Ocean. Period 2005-2009. Figura 16. Porcentaje de las longitudes totales (TL) de Merluccius australis obtenidas de las capturas comerciales en el Océano Atlántico Sudoccidental. Período 2005-2009.

Age 1 2 3 4 5 6 7 8 9 10 11 12 13+ 2005

2006

2007

2008

Year

2009

2010

2011

Figure 17. Catch at age of Merluccius australis in the Southwest Atlantic Ocean. Period 2005-2011. Figura 17. Captura por edad de Merluccius australis en el Océano Atlántico Sudoccidental. Período 2005-2011. lower than -18 °C (Bertolotti et al., 2001). Factory Most Southern hake are processed as headed fleets take 51% of the total catch (Figure 19). Most and gutted product (H&G), but cheeks and sever- Southern hake caught in SAO are landed in al meat cuts are also produced. These products Ushuaia, which is the most important harbor for are sold to Europe, with Spain being the principal these fleets (Gorini et al., 2014). market. 50 REV. INVEST. DESARR. PESQ. Nº 28: 37-53 (2016)

15,000

10,000

)

Landings (t 5,000

0 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 Year

Figure 18. Merluccius australis annual landings in the Southwest Atlantic Ocean. Period 1986-2015. Figura 18. Desembarques anuales de Merluccius australis obtenidos en el Océano Atlántico Sudoccidental. Período1986-2015.

Factory 51% REFERENCES Surimi 7% AGUAYO-HERNÁNDEZ, M. 1995. Biology and fis- heries of Chilean (M. gayi and M. aus- tralis). In: ALHEIT, J. & PITCHER, T. (Eds.). Hake: Biology, fisheries and markets. Freezer Chapman & Hall, London: 305-337. 42% AGUAYO, M. & ZULETA, A. 1988. Captura total Figure 19. Merluccius australis catch declared per fleet. permisible del recurso merluza del sur, 1988. Taken and redrawn from Gorini et al. (2014). Inf. Téc. Inst. Fom. Pesq., 26 pp. Figura 19. Captura de Merluccius australis declarada por tipo de flota. Tomado y modificado de Gorini et al. ALVERSON, D.L. & PEREYRA, W.T. 1969. (2014). Demersal fish explorations in the Northeastern Pacific Ocean. An evaluation of exploratory fishing methods and analytical ACKNOWLEDGEMENTS approaches to stock and yield forecast. J. Fish. Res. Board Can., 26 (8): 1985-2001. ANGELESCU, V. & PRENSKI, L.B. 1987. Ecología The authors would like to express their grati- trófica de la merluza común del Mar tude to Carina Fishbach and Marcela Ivanovic for Argentino (Merlucciidae, Merluccius hubbsi). providing helpful suggestions and to Marina Parte 2. Dinámica de la alimentación, analiza- Sabatini for her valuable improvements in the da sobre la base de las condiciones ambienta- manuscript. les, la estructura y las evaluaciones de los GIUSSI ET AL.: BIOLOGY AND FISHERY OF SOUTHERN HAKE - SAO 51

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