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Theme Session on Mid-ocean ridges and seamounts: oceanography, ecology, and

exploitation (C)

ICES CM 2008/C:03

Not to be cited without prior reference to the authors

By-catch of cold-water corals from an Experimental Trawl

Survey in Corner Rise and New England Seamount Complex

(NAFO Regulatory Area. Divs. 6EFG) during year 2004

by

F.J. Murillo1, P. Durán Muñoz1, M. Mandado 2, T. Patrocinio1 and G. Fernández1

1Instituto Español de Oceanografía, Vigo, Spain 2 IPD, Madrid, Spain

ABSTRACT

By-catch of cold-water corals from a Trawl Experimental Survey developed during 2004 in three NAFO Seamounts was examined (Corner Rise and New England Seamount Complex). Three hauls were carried out over two peaks located in New England Seamount Complex (Divs. 6EF). In this area, catches of commercial resources were negligible and by-catch of corals was recorded (degraded pieces of dead Enallopsammia sp and Keratoisis sp and few live corals like Solenosmilia variabilis, Metallogorgia

melanotrichos, Paragorgia johnsoni, etc.), showing some interaction between fishing and vulnerable habitats and that trawl fishing in the area is unfeasible. Ninety-two hauls were carried out over one peak located in Corner Rise Seamount Complex (Div. 6G), with big catches of alfonsino (Beryx splendens), but only six hauls showing coral records (Enallopsamia rostrata, Solenosmilia variabilis, Madrepora

oculata, Acanella eburnea and Placogorgia terceira) and in less quantities in comparison with Divs. 6EF. The low by-catch of corals in the Div. 6G peak could be related with their less rough bottom feature and with the previous alteration of sessile epifauna due to intense fishing activity developed during the last decades of XX Century. The results of the Experimental Survey indicate that the impact of trawling on seamounts could be important and that the closed area agreed in 2007 to protect the bottom habitats of the seamounts within NAFO Regulatory Area (Divs. 6EFG) should be maintained and improved. Keywords: NAFO Regulatory Area, North-west Atlantic Ocean, Corner Rise Smt., New England Smt., trawl, cold-water corals, by-catch. Contact author: F. J. Murillo. Instituto Español de Oceanografía. Programa de Pesquerías Lejanas. C.O. de Vigo. Apartado 1552. ESPAÑA. [TL: +34 986 492111, e-mail: javier.murillo@vi.ieo.es]

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INTRODUCTION

Seamounts provide a unique deep-sea environment due to the topographically-enhanced currents in their vicinity (Roden, 1986) and benthic environment is also distinct from that found on the surrounding seafloor, and may be disturbed to anthropogenic activities like bottom fishing. Due to the enhanced currents, the benthic communities around seamounts are typically dominated by corals and other suspension feeders (Rogers, 1994). Seamounts are widely recognized as areas of high productivity, and the focus of important commercial fisheries based on fish species that form large aggregation in association with them (Clark and O’Driscoll, 2002). However, by-catch of vulnerable benthic invertebrates in seamount commercial fisheries is generally poorly studied (Waller et al., 2007). Following the United Nations General Assembly Resolutions (UNGA, 2005; UNGA, 2007), several management measures in order to protect vulnerable ecosystems in the high seas, are being implemented by Regional Fisheries Management Organizations. In this way, in year 2007, several seamounts located in North-west Atlantic, including New England and Corner Rise Seamounts, were closed by NAFO to all fishing activities involving demersal fishing gears (NAFO, 2006). In year 2004, before the aforementioned closure enforcement, an Experimental Trawl Survey was carried out in fishing grounds (NAFO Regulatory Area: Div. 6EFGH & 4XWVs) considered non-habitual for the NW Atlantic Spanish fleet. This kind of cooperative surveys (Durán Muñoz and Román, 2000) are research initiatives carried out in collaboration with the fishing industry, with the aim to obtain data on distribution and biology of fisheries resources and to study the interactions between commercial fishing, gears and habitats (Durán Muñoz et al., 2007). Results from the 2004 Experimental Trawl Survey were presented to the 2005 NAFO Scientific Council Meeting (Durán Muñoz et al., 2005) focused on fish resources and including brief results on benthic invertebrate by-catch. In addition, we present here a detailed review of the cold-water coral by-catch information collected during the expedition, in order to make this data available to the ICES-ASC, contributing to improve the knowledge on the effects of fishing in the seamounts within NAFO regulatory Area. This review was made under the Spanish ECOVUL/ARPA interdisciplinary project.

MATERIAL AND METHODS

During last Quarter of year 2004, a two month Experimental Survey was carried out in NAFO Regulatory Area (Div. 6EFGH & 4XWVs) and adjacent international waters (Figure 1), with one polyvalent trawler, using “Gloria” pelagic trawl gear (60-135 mm cod end) and “Pedreira” trawl gear (130 mm cod end). A scientific observer was on board. Among other information, location, time, water temperature (by means of Pro-log attached to the net), depth, catch and discards (paying special attention to invertebrate by-catch) were noted by the observer, haul by haul. Fish species mmeasurements by sex were taken at random. Biological samples were made (stratified by length), according with IEO methods. Invertebrate’s samples were preserved as vouchers for subsequent definitive identification in the laboratory. A summary of the biological data collected is in Table 1. A total of 126 trawl hauls were carried out during the survey, which 119 were valid hauls: 95 short duration hauls (1.2 hr mean duration) with “Pedreira” gear, just over seamounts and 31 long duration hauls (11.2 hr mean duration) using “Gloria” gear far away from bottom features, between 600-1400 m and 200-800 m depth approx., respectively. In this document, for the study of fisheries resources, we analyze only the valid hauls, but for results on coral by-catch we analyze all the hauls (valid+null), because null hauls also could contain corals by-catch. Nine seamounts were explored by means of echo-sounder (SIMRAD ES-380), spending 106’5 hours, but only in three of them, fishing operations using “Pedreira” gear were carried out just over the peaks. The “cucharada” fishing technique (Gonzalez-Costas and Lorenzo, 2006) was used in order to avoid gear damage and minimize the contact with the bottom. Map of Figure 2 shows the location of the peaks where this gear and technique was employed.

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RESULTS

Fisheries resources

Sampling was conducted in a wide bathymetrical range (from 200 to 1400 m depth) and covered a large geographical area (Figure 1). Table 2 shows the effort by Division and fishing gear used. Taking into account the total of the 119 valid fishing hauls, 76% of the trawling hours corresponded to Gloria gear and 24% to Pedreira gear. Tables 3 and 4 present the catches obtained by gear for the main species caught. Alfonsino (Beryx splendens) was the main fishery resource (38% of the total catch for Gloria gear and 93% for Pedreira gear) showing the highest catch rates in Div. 6G. In this Div., the highest values of CPUEs were obtained when fishing with Pedreira gear at depths from 600 to 800 m (Table 5) and water temperature values from 11ºC to 17ºC approx. (Figure 3). Catches in other surveyed Divs. were in general scarce. Figure 4 shows the length distributions for those species by gear. In the Pedreira Hauls (Div. 6G: 600-1200 m depth), length range of alfonsino (total length) was comprised between 27-55 cm (mode = 42 cm). In the Gloria hauls (Div 6G: 600-800 m depth) the length range was comprised between 24-52 cm (mode = 45 cm). It is worthy to noted, that juvenile alfonsinos (10-18 cm length; mode = 13 cm) were recorded in some hauls carried out with Gloria gear in Divs. 6E, 6F, 4Vs (200-400 m depth) and outside NAFO Area (200-800 m depth). These individuals were absent in the hauls carried out in the Div 6G. Table 6 shows the length-weight relationships for the main commercial species [Weight (g) = a . Length (cm) b]. In two hauls carried out in Div. 6G, lost pots in good conservation state were found entangled in the Pedreira gear, indicating recent bottom fishing activity in the seamount surveyed. During the survey, by-catches of mammals, seabirds or sea turtles did not take place. Conversely, some by-catches of cold-water coral were recorded in some Pedreira hauls. These records are analyzed in detail in the next chapter. In addition small by-catches of other benthic taxa such as porifera, echinodermata and polichaeta, were also recorded in these hauls (Duran Muñoz et al., 2005).

By-catch of cold-water corals Table 7 shows the number of hauls with coral by-catches. Coral records did not occur in any fishing operations carried out by means “Gloria” gear. On the other hand, corals were recorded in 9 hauls using “Pedreira” gear just over three peaks located in New England and Corner Rise Seamount Complexes. In the remainder 86 hauls carried out with this gear over peaks, no coral by-catch was observed.

New England Seamount Complex (NAFO Divs. 6EF)

In the Divs. 6EF, a total of three short hauls were carried out with “Pedreira” gear just over two peaks. Fishing operations were very difficult, because rough bottom features were found. On the other hand, catches of main commercial fish species were negligible (Durán Muñoz et al., 2005) and some by-catch of corals was recorded (Table 7). The most common coral by-catch recorded in Div. 6F was the colonial scleractinian Enallopsammia sp (Table 8). Most of the by-catch of this specie corresponded to pieces of degraded dead skeletons (like sub-fossil), though several fragments presented recent scars showing that they could belong to a coral structure. Also the base of a big Keratoisis sp like sub-fossil was caught. Another records of live corals, include the scleractinian Solenosmilia variabilis, gorgonians (Metallogorgia melanotrichos, Paragorgia johnsoni and Lepidisis sp.) and antipatharians. In Div 6E (Table 8), by-catch of corals was less important. Corals observed were the scleractinian Solenosmilia variabilis (dead) and the gorgonian Thouarella grasshoffi.

Corner Rise Seamount Complex (NAFO Div. 6G)

On the Div. 6G, fishing operations using “Pedreira” gear were carried out over one peak exclusively. The peak showed a rough feature. Nevertheless, trawl fishing over the summit were less difficult than in Divs. 6EF, and catches of alfonsino were considerable. In this seamount, 92 short hauls using “Pedreira”

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gear were carried out, and only in 6 of them slight amount of corals were recorded. Corals observed were a piece of Enallopsamia rostrata, Solenosmilia variabilis, Madrepora oculata, Acanella eburnea, Placogorgia terceira and antipatharians (Table 8).

DISCUSSION

The results of the 2004 Trawl Exploratory Survey show that, at least, in two peaks located in New England Complex (Divs. 6EF), trawl fishing operations are unfeasible, due negligible catches of commercial resources and occurrence of by-catch of corals, which indicates some interaction between fishing and vulnerable habitats. On the other hand, in one peak of Corner Rise Complex (Div. 6G), despite the intense fishing activity directed to alfonsino along the last decades of XX Century in the area, high catches of this fish species were obtained, but in the 7% of the fishing operations, by-catch of cold-water corals was recorded. This fish species is relatively fast growing and not long-lived (10-15 years) and thus do not posses the biological traits typical of many other deep-sea species. Alfonsino appears to aggregate near certain NAFO seamounts, making it likely vulnerable to exploitation. The less by-catch of corals recorded - in comparison with New England Complex - could be related both with the more friendly bottom feature (Figure 5) of the peak (and the consequent success of the “cucharada” fishing technique), and/or with the previous alteration of sessile epifauna due to the intense fishing activity developed in the past (Vinnichenko, 1997). Moreover, Waller et al. (2007) using a remotely operated vehicle (ROV) documented evidence of large-scale trawling damage on Div. 6G. Generally coral by-catch obtained in seamounts during the 2004 trawl experiment, corresponded to dead skeletons. It is accepted, that the degradation of coral reefs could be due to either natural or anthropogenic factors (Mortensen et al., 2007). Nevertheless, coral rubble provides appropriate substrate to epifauna and this is very relevant in terms of associate biodiversity. Fishing techniques used over seamounts are totally different from the techniques used in sedimentary seabed over continental slope. Multidisciplinary studies (Duran Muñoz et al., 2008) shown that the habitats in the sedimentary seabed was generally very different from the habitats observed in hard substrate seabed. Consequently, is expected different kind of interaction between gears and habitats. In seamount fisheries, obviously, fishing techniques have been designed to minimize bottom contact, with the objective to avoid gear damage and to increase the catches of fish aggregations, located generally no very close to the bottom of the summit. Nevertheless, result difficult to achieve a total success in this objective and in certain number of hauls (depends on several factors like the skipper experience and ability, the fishing technique used, etc.), trawl gear could contact with the bottom, and corals could be damaged. Data presented here are based on experimental trawls. Despite that the aforementioned technical factors and the fishermen experience could be improved, results of this trawl experiment supported by the evidence of bottom seamount habitat alteration documented by means ROV, indicate that the impact of trawling on seamount complex could be important, with the coral substrate and associated community removed from the most heavily fished seamounts (Koslow et al., 2001). This seems that the closed area agreed in 2007 to protect the bottom habitats of the seamounts within NAFO Regulatory Area (Divs. 6EFG) should be maintained and improved. On the other hand, the presence of lost pots observed in this area, could indicate the existence of some other kind of bottom fishing activity in Division 6G, which effects have not still been documented.

ACKNOWLEDGEMENTS

The 2004 Trawl Experimental Survey was funding by Spanish Government. Secretaría General de Pesca (former SGPM. Ministerio de Agricultura, Pesca y Alimentación). Our sincerely thanks to the vessel crew, for assistance in the data collection onboard. The review of the coral samples was made under the ECOVUL/ARPA interdisciplinary project, funding by SGPM and Instituto Español de Oceanografía.

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REFERENCES

CLARK, M.R. and R.L. O’ DRISCOLL. 2002. Deepwater fisheries and their impacts on seamount habitat in New Zealand. J. Northw. Atl. Fish. Sci, 31: 441-458. DURÁN MUÑOZ, P. and E. ROMÁN, 2000. Spanish Experimental Fishings: A cooperative research initiative between scientists and the local fishing industry. ICES CM 2000/W: 03. DURAN MUÑOZ, P., M. MANDADO, A. GAGO, C. GÓMEZ, and G. FERNÁNDEZ. 2005. Brief results of a trawl experimental survey at NW Atlantic. NAFO SCR Doc. 05/32, Serial No. N5095. DURÁN MUÑOZ, P., M. SAYAGO-GIL, T. PATROCINIO, A. SERRANO, F.J. MURILLO, S. PARRA, L.M. FERNÁNDEZ SALAS, M. SACAU, V. DÍAZ DEL RÍO and X. PAZ. 2007. ECOVUL/ARPA Interdisciplinary Project: Looking for a model to study the interaction between deep-water bottom fisheries and their supporting high seas ecosystems. ICES CM 2007/R: 01. DURÁN MUÑOZ, P., M. SAYAGO-GIL, J. CRISTOBO, S. PARRA, A. SERRANO, V. DÍAZ DEL RÍO, T. PATROCINIO, M. SACAU, J. MURILLO, D. PALOMINO, M. DOMÍNGUEZ and L.M. FERNÁNDEZ-SALAS. 2008. A practical example of mapping in order to select closed areas to protect cold-water corals in the high seas (Hatton bank ICES VIb1 & XIIb). ICES CM 2008/G:01 GONZÁLEZ-COSTAS, F. and J.V. LORENZO. 2007. Spanish fisheries information in Corner Rise Seamount Complex (NAFO Divisions 6GH). NAFO SCR Doc. 07/26, Serial No. 5377 KOSLOW, J.A., K. GOWLETT-HOLMES, J.K. LOWRY, T. O’HARA, G.C.B. POORE and A. WILLIAMS. 2001. Seamount benthic macrofauna off southern Tasmania: community structure and impacts of trawling. Marine Ecology Progress Series 213: 111-125. MORTENSEN, P.B., L. BUHL-MORTENSEN, A.V. GEBRUK, and E.M. KRYLOVA. 2007. Occurrence of deep-water corals on the Mid-Atlantic Ridge based on MAR-ECO data. Deep-Sea Research II (2008), 142-152. NAFO. 2006. Northwest Atlantic Fisheries Organization. Report of the Fisheries Commission 28th Annual Meeting, 18-22 September 2006. Darmouth, Nova Scotia, Canada. NAFO/FC Doc. 06/14. Serial No. 5312, 58 pp. RODEN, G.I. 1986. Aspects of oceanic flow and thermohaline structure in the vicinity of seamounts. In: Uchida R.N., Hayasi, S., Boehlert, G.W. (eds). Environment and resources of seamounts in the North Pacific. NOAA Tech Rep NMFS 43: 3-12. ROGERS, A.D. 1994. The biology of seamounts. Advances in Marine Biology 30:305-350. ROGERS, A.D., M.R. CLARK, J.M. HALL-SPENCER and K.M. GJERDE. 2008. The Science behind the Guidelines: A Scientific Guide to the FAO Draft International Guidelines (December 2007) For the Management of Deep-Sea Fisheries in the High Seas and Examples of How the Guidelines May Be Practically Implemented. IUCN, Switzerland, 2008. UNGA. 2005. Resolución aprobada por la Asamblea General. 59/25. La pesca sostenible, incluso mediante el Acuerdo de 1995 sobre la aplicación de las disposiciones de la Convención de las Naciones Unidas sobre el Derecho del Mar de Diciembre de 1982 relativas a la conservación y ordenación de las poblaciones de peces transzonales y las poblaciones de peces altamente migratorios, e instrumentos conexos. 17 de enero de 2005. Ref.: A/Res/59/25

UNGA. 2007. Resolución aprobada por la Asamblea General. 61/105. La pesca sostenible, incluso mediante el Acuerdo de 1995 sobre la aplicación de las disposiciones de la Convención de las Naciones Unidas sobre el Derecho del Mar de Diciembre de 1982 relativas a la conservación y ordenación de las

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poblaciones de peces transzonales y las poblaciones de peces altamente migratorios, e instrumentos conexos. 6 de marzo de 2007. Ref.: A/Res/61/105.

VINNICHENKO V.I. 1997. Russian Investigations and deep water Fishery on the Corner Rising Seamount in Subarea 6. NAFO Scientific Council Studies Number 30: 41-49. WALLER, R., L. WATLING, P. AUSTER, and T. SHANK. 2007. Anthropogenic impacts on the Corner Rise Seamounts, north-west Atlantic Ocean. J. Mar. Biol. Ass. U.K. 87: 1075-1076.

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Table 1.- 2004 Trawl Experimental Survey. Number of samples, individuals and otoliths collect, by species.

Table 2.- 2004 Trawl Experimental Survey. Fishing effort in hours trawling by Division and gear.

Table 3.- 2004 Trawl Experimental Survey. Pedreira gear: Total catch (kg) for the main species by Division.

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Table 4.- 2004 Trawl Experimental Survey. Gloria gear: Total catch (kg) for the main species by Division.

Table 5.- 2004Trawl Experimental Survey. CPUE (Kg/hr) of alfonsino in Div. 6G, by depth range and fishing gear used.

Depth range (m) approx. Pedreira gear Gloria gear

200-400 -- <0.05 401-600 -- <0.05 600-800 6,412 64

801-1000 4,067 -- 1001-1200 804 -- 1201-1400 228 --

Table 6.- 2004Trawl Experimental Survey. Length-weight relationship parameters for the main commercial fish species.

Table 7.- 2004 Trawl Experimental Survey. Pedreira hauls carried out in New England and Corner Rise Seamount Complex: Total hauls and hauls with cold-water coral presence.

New England Smt.

Complex Corner Rise Smt.

Complex

Div 6E Div. 6F Div.6G

Nº of hauls carried out 1 2 92 Nº of hauls with coral presence 1 2 6

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Table 8.- 2004 Trawl Experimental Survey. By-catch of cold-water corals (kg) in New England and Corner Rise Seamount Complex. (1) alive; (2) dead; (3) like sub-fossil; (4) unknown status.

New England Smt. Complex

Corner Rise Smt. Complex Cold-water coral species

Div 6E Div. 6F Div.6G

Enallopsammia rostrata -- -- 0.022(1)

Solenosmilia variabilis 0.57(2) 0.471(1) 0.225(4)

Madrepora oculata -- -- 0.015(4)

Enallopsammia sp -- 70.422(3) --

Keratoisis sp -- 2(3) --

Paragorgia johnsoni -- 0.156(1) --

Acanella eburnea -- -- 0.02(1)

Lepidisis sp. -- 1(1) --

Placogorgia terceira -- -- 0.004(1)

Thouarella grasshoffi 0.011(1) -- --

Metallogorgia melanotrichos -- 0.02(1) --

Antipatharia indet. 1 -- 0.150(1) --

Antipatharia indet. 2 -- -- 0.005(1)

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Figure 1.- NAFO Convention Area. The 2004 Experimental Trawl Survey was carried out within the Regulatory Area (Div. 6EFGH & 4XWVs) and adjacent international waters. Circles show the location of study area (approx.).

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Figure 2. - 2004 Trawl Experimental Survey. Location of the Pedreira hauls carried out in New England (Div 6EF) and Corner Rise (Div. 6G) Seamounts complexes.

Figure 3. - 2004 Trawl Experimental Survey. Relation between water temperature and depth obtained in Corner Rise Seamount complex (Div. 6G) by means of a Pro-log attached to the fishing gear.

Div. 6G

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Figure 4.- Length distributions for the main fish species by gear.

Figure 5 - 2004 Trawl Experimental Survey. Bottom profile obtained in Corner Rise Seamount complex (Div. 6G) by means the vessel echosounder.