APPENDIX V

REPORT OF THE WORKSHOP ON CONSERVATION AND MANAGEMENT OF DEEPWATER CHONDRICHTHYAN FISHES

Portobello Marine Station, University of Otago
Dunedin, New Zealand
27-29 November 2003

S.B. Irvine
Deakin University and CSIRO Marine Research
GPO Box 1538 Hobart, Tasmania, Australia 7001
<[email protected]>

1. Workshop objectives

This meeting was held to provide an opportunity for specialists to present information on the ecology, taxonomy, stock status and conservation threats to deep-sea chondrichthyans. Recommendations for the conservation and management for these highly vulnerable fish were discussed, many of which are threatened by deep-sea fisheries.

The meeting was convened within the context of the FAO International Plan of Action for Conservation and Management of Sharks (IPOA-SHARKS). This IPOA recommends that all States contributing to fishing mortality of an elasmobranch species or stock should participate in their management. Funding for the meeting was provided by the FAO through a trust fund from the Japanese Government (GCP/INT/715/JPN), the David and Lucile Packard Foundation and the Department for Environment Food and Rural Affairs, U.K.

The agenda of the meeting is listed in Appendix I and those who participated in Appendix II. The Workshop also undertook assessments for the 2004 IUCN Red List of Threatened Speciesä which were completed for as many deep-sea chondrichthyans as possible. A baseline was established for monitoring improvements to our knowledge of this group of fishes and changes in their overall conservation and management status.

2. Background

The continental slope habitat represents only 13 percent of the ocean bottom (Angel 1997) although it supports the greatest diversity of chondrichthyan species. Many species have a limited depth range and some have a narrow geographic range.

Relatively few studies on deepwater chondrichthyans exist in the scientific literature and the majority deal with squaloids, reflecting their greater commercial importance. Deepwater chondrichthyans are a large bycatch and by-product component of many commercial fisheries that predominantly target teleosts and crustaceans. However, target fisheries for deepwater chondrichthyans are becoming increasingly important, driven by the international demand for their products, particularly liver oil. It has been well documented that chondrichthyans are particularly vulnerable to fishing pressure owing to their slow growth, late attainment of sexual maturity and low reproductive output (Stevens et al. 2000). Deep-sea chondrichthyan fishes are defined as bathyal species occurring at depths >200 m. Some oceanic pelagic species may descend into these deeper waters, but they were excluded from this Workshop. Data on deepwater chondrichthyan catches are sparse as landings reports rarely provide accurate species composition information in detail. In order to use landings data for assessment purposes, it is essential that the species involved can be identified and this requires all species to have been adequately described. Numerous deepwater genera, including Apristurus and Centrophorus, are currently under taxonomic revision.

3. Meeting structure

A total of 35 participants from 12 countries attended the workshop. The meeting was opened on Thursday 27 November by two keynote addresses (summarized below), and over two days 19 oral and 8 poster presentations were given under the following themes:

• life history
• conservation and management
• taxonomy
• utilisation and threats and
• stock assessment.

On Saturday 29 November, time was allocated for general discussions and the group drafted the conclusions of the workshop. The 2004 IUCN Red List of Threatened Speciesä assessment of deepwater chondrichthyans was undertaken on Saturday afternoon and many participants continued this work on Sunday 30 November.

4. Summary of keynote addresses

4.1 Professor Sho Tanaka (Tokai University): A survey of the fishery and biological situation on deep-sea chondrichthyan fish in Suruga Bay, Japan

Deep-sea sharks and chimaeras occur as an incidental catch of Japanese trawlers operating on the continental slopes. In his address Professor Tanaka gave an account of the distribution and biology of deep-sea and bottom-dwelling sharks, with some discussion on the changes in species composition and catch rate.

It has been found that deepwater sharks have a high concentration of mercury, PCBs and organochlorines, independent of their proximity to sources of anthropogenic contamination. These high levels of contaminants arise from the longevity of chondrichthyans and their high trophic level. Average concentrations on contaminants often exceed (sometimes by double) the World Health Organization’s standards. Squaloids have been shown to accumulate a high level of contamination, which possibly manifests in high levels of reproductive malformation (e.g. hermaphroditism).

4.2 Dr Kazunari Yano (Seikai National Fisheries Research Institute): Aspects of the biology of deep-sea sharks

This presentation discussed the biological aspects of deep-sea sharks, including rare (e.g. Mitsukurina, Chlamydoselachus) and endemic species (e.g. of the genera Gollum and Trigonognathus) collected from several areas in the world. The different types of embryonic development and reproductive modes observed between species were described and the usually long gestation periods and small litter sizes noted.

5. Overview of presentations

Theme 1: Life history

Ten oral presentations and five posters were presented whose topics included descriptions of the depth distributions and habitat utilisation, reproductive biology, age and growth, and feeding habits. Information was reported on the general depth distributions for a variety of species. Chondrichthyans, especially sharks, are apex predators occupying the highest trophic levels. Their depth distributions may be linked to surface water primary production as shark numbers are highest in the deeper waters areas where surface water primary production is highest. Geographic and, or, depth segregation of different size, age or reproductive stages within a population were noted; e.g. juveniles of the species have not been found on the European continental slope.

Reproductive information, including litter size (or number of egg cases), size at birth and size at maturity was reported for numerous species. Two reproductive strategies were noted for dogfishes (Order Squaliformes): (a) small litter sizes and continuous reproductive cycle and (b), larger litter sizes and a non-continuous cycle (i.e.a rest phase between pregnancies). Reproductive seasonality was not reported for any deepwater chondrichthyan fishes and information on egg-laying rates for deepwater skates, cat-sharks or chimaeras remains unknown.

Age estimates, including age at maturity, are obtained through dorsal-fin spine band counts and high longevity estimates (up to 54 years) were reported for Centroscymnus crepidater, with maturity occurring at 9-15 years. Current attempts at validating the periodicity of band deposition were reported.

Information of the feeding habits of many chondrichthyans was presented. Most papers gave a detailed prey list and reported a high trophic order. Most species appear to be opportunistic feeders although ontogenetic variation in diet and specialised feeding are also evident

Theme 2: Conservation and management

Dr Rachel Cavanagh, in the only paper presented under this theme, reported the necessity of implementing appropriate conservation and management measures. Knowledge of the status of most deep-sea chondrichthyans is seriously limited, and most animals fall into the data deficient category. However, it is striking that several deep-sea chondrichthyans that have been assessed fall into critically endangered or endangered categories. It was noted that the IUCN Ref List of Threatened Specie ä is a widely recognised and powerful tool that can be used to promote improvements in the fisheries management of these biologically vulnerable species. An overview of the structure for a Red List assessment was given using Centrophorus harrissoni and C. uyato - two critically endangered dogfishes - as examples.

Theme 3: Taxonomy

Two oral papers and one poster were presented in this session in which it was noted that deep-sea chondrichthyan fishes of the world consist of an eclectic mix of biogeographic members varying from narrow-ranging regional endemic species to some of the most widespread fishes in the world. Evidence of a greater level of range-restriction was also discussed. An overview of the species composition in Sagami Bay, Japan was given and included accounts of species that were not been previously known in the area. Sampling data suggest that Squalus mitsukurii have a seasonal migration horizontally and vertically in Sagami Bay; no S. mitsukurii were found in winter samples.

Information on chondrichthyans available to a deepwater fishery operating in the San Andrés Archipelago, western Caribbean Sea was also presented. Six deep-sea species were reported, of these, four were new records for Colombia.

Theme 4: Utilization and threats

Three oral papers and one poster presented information on the capture and utilisation of deepwater chondrichthyans off Namibia, New Zealand, Indonesia and Australia. Species that were previously discarded in Namibia, New Zealand and Australia now have good market demand and are landed for human consumption. Case studies of Namibia and Australia demonstrated that a small number of vessels operating target fisheries can quickly deplete previously unexploited stocks. Recovery of depleted stocks is likely to be extremely slow because of the sharks’ life history characteristics.

Indonesian chondrichthyan landings are high and remain largely unreported, with little or no discarding. Marketing of flesh, liver oil and fins are common, and in some areas of Indonesia the large oocyte (egg) of Centrophorus species is a delicacy.

Theme 5: Stock assessment

Three oral papers and one poster presented information on chondrichthyan population and stock structures. Ecological risk to chondrichthyan populations from commercial fishing can be assessed through their biological productivity, catch susceptibility, trends in abundance and trophic position.

Biological productivity is related to generation time and reproductive output from each generation. This can be derived from natural mortality and reproductive information - fecundity and frequency of spawning events. Vulnerability of capture is similar to the concept of ‘catchability’ but should also include considerations of bycatch, which may, or may not, be discarded. Post-capture mortality is the proportion of the animals that die from being caught in the fishing gear. Populations with a declining trend in biomass can be classed at higher risk than those with stable, fluctuating or rising trends. Trophic position is also an indicator of potential risk as species with a high trophic position are more vulnerable to the effects of ecological cascade than those in a low position.

In areas where baseline (precommercial exploitation) data exists, mean relative catch rates have severely declined. In this context, abundance measures were reported for three species of chondricthyans in the Mediterranean Sea.

6. General discussion and recommendations

6.1 Identification of management problems

Deepwater chondrichthyans do not require any unique management measures compared to other fisheries. However, management is more complex and critical as the available stock and sustainable yield is much lower for all chondrichthyan fishes, especially those that inhabit relatively unproductive deepwater. Monitoring of fish stocks is also challenging as some fisheries are on the high seas where States’ authority over their flagged vessels may not apply and the only control may be through port states and other indirect means.

Management problems arise when a population covers an area that is fished by many states. Effective management of such stocks require agreement among fishing nations, or management through regional fisheries management organizations. In addition, the depth and spatial segregation that often occurs within a chondrichthyan population (usually by sex, age/size and reproductive stage) makes different components of the population available to the fishery. This makes it relatively easy to remove an entire and possibly vital component of a population (e.g. all the pregnant females) by a relatively localized fishery.

Reliable catch information is rarely available. The landing of processed animals (trunks, etc.) makes it extremely difficult to identify the species composition of the catch and thus obtain species composition data except by genetic techniques. Lamentably, catch statistics for many species are often collated under one name e.g. "shark various", "black shark", "dogfish", "ghost shark", "skate", "ray", etc.

6.2 Management requirements

Effective management requires good baseline data and this rarely exists for chondricthyan fishes and therefore a significant increase in investment research for this purpose is needed. Although research needs to increase in any event, management, in the meanwhile, should follow the precautionary approach and implement appropriate regulations immediately.

Ideally, deepwater fisheries should not be initiated until baseline data is obtained from fisheries-independent surveys. Human and funding resource limitations make this approach difficult in many nations, thus managers and scientists need to work in conjunction with fishers to obtain the maximum data for all exploratory fisheries so fish stocks can be monitored.

Closed fishing areas and marine protected areas are an important fisheries management and biodiversity conservation tool. However, it is important to identify candidate areas that offer the greatest benefit. This requires an understanding of species composition, stock structure and movement patterns. Managers may use this information to determine critical habitat size and location and to decide whether there are any benefits from seasonal closures. Larger areas should be allocated in those areas where collection of this information is not possible, especially if fisheries are not yet established.

Adequate catch monitoring is essential for effective management. Education programs aimed at managers and stakeholders are required to outline the vulnerability of these fishes compared to other taxa. Workshops can be used to transfer expertise to managers and scientists including through the teaching of appropriate monitoring tools and methods.

The species composition of the catch is currently impossible to determine if the fish are processed at sea, e.g. by removal of fins, tails and head. Regulations for chondrichthyan fisheries should require the retention of heads, fins and tails and prohibit the landing of fins, skate wings and livers without the accompanying carcass.

7. Future research

The Workshop identified a number of areas of scientific research that needs to focus on:

i. Taxonomy

Many species taken by commercial fisheries remain undescribed and a large number of sympatric species complexes are unresolved. The resolution of these issues would enable the preparation of accurate identification keys and guides that are necessary for data collection and enable the definition of species and stock distributions.

A regional approach to tackling taxonomic problems should be a priority with subsequent collation of the information that is obtained. The use of genetic techniques may be required to separate some sympatric species and an adequate number of voucher specimens need to be collected so key morphological characteristics can be identified. Photography can be used is an important identification tool. Separate head and fin photographs are beneficial and colourations of fresh animals should be noted.

ii. Life history

Knowledge of longevity and age-at-maturity estimates is essential for stock assessments. Ageing techniques have been tried for squaloids, chimaeras and rajids, although band count periodicity has not been validated. Dorsal-fin spines (squaloids and chimaeras) and caudal thorns (rajids) appear to yield better results than the poorly calcified vertebrae.

Age validation may require investigation into the feasibility of radiocarbon dating or radiometric isotope analysis. The cue for growth in deepwater chondrichthyans may be influenced by seasonal food availability rather than seasonal temperature cycles, thus information on trophic ecology is required.

A knowledge of trophic levels would also allow basic definition of community structure and provide data for ecosystem modelling. Consumption rates, interspecies dynamics, energy partitioning between co-occurring species and the ontogenetic regional and seasonal variations are largely overlooked and unrecorded. Information on basic metabolic physiology is also required.

iii. Reproductive biology

Knowledge of a species’ reproductive biology (e.g. annual fecundity, maturity/maternity ogives, birth size) is central to understanding their life history. Annual fecundity, duration of development, inter-breeding intervals and natural mortality are all required, but usually are poorly understood. Reproductive cycles remain undefined and the lack of seasonality in many species prohibits the use of traditional analysis. Investigation into the use of specific endocrinology may be required. The life strategy benefits of the trade-offs between growth and reproduction in an energy-poor environment are unknown.

iv. Stock structure

Resource management is extremely difficult without knowledge of the population structure. Depth distribution studies require deeper sampling to accurately define depth ranges and possible depth-dependent segregation by sex. Many populations may occur below fishing depth, e.g. bathyrajids are not often recorded at depths of less than 2000 m.

Tagging in the deep sea is in its infancy and although it is possible it remains difficult and uncertain as to its effects. Future work directions may involve the use of innovative technology, e.g. electronic tagging, pop-off satellite tags, listening stations, ‘at-depth’ tagging. All of these are expensive but when successful can produce results of great value.

v. Bycatch survivability

Research is needed on the survival of discards. Unwanted juveniles of larger species and smaller species are usually discarded. Different fishing methods result in different discard mortalities. With regard to trawling, analysis of the catch taken in shorter tows in cooler waters (e.g. southern Tasmania, Australia) show that a high proportion of dogfishes that land on deck are still alive. Assessments are required of the survivability of these animals if they are released quickly.

8. Conclusions

Deepwater chondrichthyans may not sustain the current levels of exploitation due to their low fecundity, late attainment of sexual maturity, long life and extended gestation periods (some with a resting stage between pregnancies). Management should follow the precautionary approach and implement regulations immediately.

9. Literature cited

Angel, M.V. 1997. What is the deep sea? In: Randall, D.J. & A.P. Farrell (eds.) Deep-sea Fishes (Fish Physiology volume 16). Academic Press. San Diego, USA.

Stevens, J.D., R. Bonfil, N.K. Dulvy & P.A. Walker 2000. The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. ICES Journal of Marine Science. 57 (3) 476-494.

10. Programme of Workshop