Deep-water Shark Research Articles

Habitat partitioning and vulnerability of sharks in the Great Barrier Reef Marine Park

Sharks present a critical conservation challenge, but little is known about their spatial distribution and vulnerability, particularly in complex seascapes such as Australia's Great Barrier Reef Marine Park (GBRMP). We review (1) the distribution of shark species among the primary habitats of the GBRMP (coral reefs, inshore/shelf, pelagic and deep-water habitats) (2) the relative exploitation of each species by fisheries, and (3) how current catch rates interact with their vulnerability and trophic index. Excluding rays and chimaeras, we identify a total of 82 shark species in the GBRMP. We find that shark research in the GBRMP has yielded little quantitative information on most species. Reef sharks are largely site-fidelic, but can move large distances and some regularly use non-reef habitats. Inshore and shelf sharks use coastal habitats either exclusively or during specific times in their life cycle (e.g. as nurseries). Virtually nothing is known about the distribution and habitat use of the GBRMP's pelagic and deep-water sharks. At least 46 species (53.5 %) are caught in one or more fisheries, but stock assessments are lacking for most. At least 17 of the sharks caught are considered highly vulnerable to exploitation. We argue that users of shark resources should be responsible for demonstrating that a fishery is sustainable before exploitation is allowed to commence or continue. This fundamental change in management principle will safeguard against stock collapses that have characterised many shark fisheries.

Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework

Abstract Marchal, P., and Vermard, Y. 2013. Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework. – ICES Journal of Marine Science, 70: 768–781. We have used in this study a spatially explicit bioeconomic modelling framework to evaluate management strategies, building in both data-rich and data-limited harvest control rules (HCRs), for a mix of deepwater fleets and species, on which information is variable. The main focus was on blue ling (Molva dypterygia). For that species, both data-rich and data-limited HCRs were tested, while catch per unit effort (CPUE) was used either to tune stock assessments, or to directly trigger management action. There were only limited differences between the performances of both HCRs when blue ling biomass was initialized at the current level, but blue ling recovered more quickly with the data-rich HCR when its initial biomass was severely depleted. Both types of HCR lead, on average, to a long-term recovery of both blue ling and saithe (Pollachius virens) stocks, and some increase in overall profit. However, that improvement is not sufficient to guarantee sustainable exploitation with a high probability. Blue ling CPUE did not always adequately reflect trends in biomass, which mainly resulted from fleet dynamics, possibly in combination with density-dependence. The stock dynamics of roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo) and deepwater sharks (Centrophorus squamosus and Centroscymnus coelolepis) were little affected by the type of HCR chosen to manage blue ling.

Complete mitochondrial genome of the megamouth shark Megachasma pelagios (Chondrichthyes, Megachasmidae)

Here we describe the complete mitochondrial genome sequence of the megamouth shark, Megachasma pelagios, which is an extremely rare species of deepwater shark. The circle genome (16,694 bp) consists of 13 protein coding, 22 tRNA, 2 rRNA genes and 1 control region. It has the typical vertebrate mitochondrial gene arrangement.

First pelagic record of the velvet dogfishZameus squamulosus(Günther, 1877) (Squaliformes) from the southwestern Indian Ocean and some notes on its regional distribution

ABSTRACT A pelagic record of a rare deep-water shark, the velvet dogfish Zameus squamulosus (Gunther, 1877), is described from the southwestern Indian Ocean. This is the first pelagic record from the western Indian Ocean and the eleventh published record of this species from the entire basin. Together with non-published records from museums and online databases the number of verified Indian Ocean records of this species currently exceeds 50 individuals. Zameus squamulosus is a benthopelagic species usually occurring on the slopes of the continents and in mid-ocean oceanic ridges, between 400 and 1450 m depth, but it makes rare incursions in open water to the limits of the epipelagic zone.

Effect of environmental variations on sharks and other top predators in the deep Mediterranean Sea over the last 60 years

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 55:239-251 (2013) - DOI: https://doi.org/10.3354/cr01137 Effect of environmental variations on sharks and other top predators in the deep Mediterranean Sea over the last 60 years J. E. Cartes1,*, E. Fanelli1, D. Lloris1, J. Matallanas2 1ICM-CSIC Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain 2Facultat de Ciències Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain *Email: jcartes@icm.csic.es ABSTRACT: The deep Mediterranean, which is characterized by high thermohaline stability, has suffered important changes in the last century, but these have seldom been analyzed with regard to megafauna. Long-term changes in fish and decapod assemblages in the Balearic Basin (western Mediterranean) were analyzed after compiling (since 1952) the species compositions of hauls taken at depths of ca. 400 to 600 m. Multidimensional scaling analysis (MDS) showed significant segregation between hauls performed in the period 1952−1964 and hauls taken later. MDS segregated hauls taken off Catalonia from those off the Balearic Islands. The most general change recorded was a drop in the occurrence of most of the dominant deep-sea chondrichthyans, especially the shark Etmopterus spinax. Environmental analyses (canonical correspondence analysis and BIOENV) suggested a direct relationship between increases in temperature and salinity in intermediate waters and the decline of deep-water sharks. Abundance of E. spinax also decreased with decreasing O2 in the Levantine Intermediate Water (LIW) that may be related to changes in LIW in the western Mediterranean since the 1950s. This is in addition to increased fishery effort as a factor explaining the drop in shark abundance. In other regions of the western Mediterranean subjected to fishery pressure, E. spinax is still dominant. We suggest that small changes, both anthropogenic and climatic, occurring in the temperature and salinity of deep-water masses since the 1950s in the Balearic Basin have changed the composition of fish (especially sharks due to their high vulnerability) and crustacean assemblages. KEY WORDS: Balearic Basin · Megafauna · Environmental change Full text in pdf format PreviousNextCite this article as: Cartes JE, Fanelli E, Lloris D, Matallanas J (2013) Effect of environmental variations on sharks and other top predators in the deep Mediterranean Sea over the last 60 years. Clim Res 55:239-251. https://doi.org/10.3354/cr01137 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 55, No. 3. Online publication date: February 06, 2013 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2013 Inter-Research.

Distribution patterns of deep-sea fish and benthic invertebrates from trawlable grounds of the Hatton Bank, north-east Atlantic: effects of deep-sea bottom trawling

Distributions of deep-sea fish, benthic invertebrates and the effects of deep-sea bottom trawling were studied based on data collected in 2005 from a joint collaboration survey undertaken between the Spanish Institute of Oceanography and a deep-sea trawler on the Hatton Bank (north-east Atlantic). A total of 163 valid bottom trawl hauls (600–1600 m) were analysed. The main trawlable grounds were located on the sedimentary seabed of the western flank of the bank (Hatton Drift). Grenadiers and smoothheads were predominant in the trawl catches (67% and 11.8% by weight respectively). Both species were abundant along the western flank. Deep-water sharks accounted for 7.4% of weight, and were abundant along the south-eastern slopes. Chimerids, lotids, morids and other deep-sea species were also taken as by-catch. Grenadiers and deep-water sharks dominated the discards. By-catches of cold-water corals were generally associated with the rocky outcrop and were more abundant at the top of the bank. Abundant by-catches of large sponges, characteristic of sponge-dominated biotopes, were taken from the eastern flank.

Genetic population structure and connectivity in a commercially exploited and wide-ranging deepwater shark, the leafscale gulper (Centrophorus squamosus)

The leafscale gulper (Centrophorus squamosus) is a wide-ranging deepwater benthopelagic shark threatened by commercial fisheries in parts of its range. Despite concerns about resource sustainability, little is known about the population structure and connectivity between critical habitats of the leafscale gulper. This study investigates the genetic population structure and the migration patterns of C. squamosus using nuclear microsatellites and mitochondrial NADH dehydrogenase subunit 2 (ND2) gene sequences. Genetic diversity was estimated and compared among sample collections from off Ireland, Portugal, the Azores, South Africa and New Zealand. The null hypothesis of genetic homogeneity among all collections was not rejected by the nuclear loci (FST (the overall genetic differentiation among sample collections) = –0.002, P = 0.88), but we found long-term genetic divergence between New Zealand and the remaining collections at the mtDNA ND2 (FCT (genetic differentation among groups of sample collections) = 0.366, P = 0.000). Migration rate estimates indicated limited female dispersal across the Indian Ocean whereas males showed less restricted dispersal. Our results are consistent with a single genetic stock of C. squamosus and the existence of sex-biased dispersal across the Indian Ocean. Widespread genetic homogeneity at nuclear loci minimizes the loss of unique adaptive genetic diversity in the event of localised depletion. However, high local fishing mortality may have far reaching impacts given the marked sex- and maturity-stage-based habitat partitioning previously reported for C. squamosus.

Reproductive strategy of the female deep-water shark birdbeak dogfish,Deania calcea: lecithotrophy or matrotrophy?

Little information is available on the maternal–embryonic relationships among sharks. Birdbeak dogfish (Deania calcea) has been described as ovoviviparous, but this term comprises a wide range of forms on how the embryos are nourished including lecithotrophy and matrotrophy. To evaluate the maternal–embryonic relationship in birdbeak dogfish we have analysed chemical features (fatty acid composition and mercury (Hg) levels) and biological characteristics (egg and embryo dry weight variation, uterus characterization). Monounsaturated fatty acids were the dominant fatty acids in eggs while polyunsaturated fatty acids (PUFA) were the dominant fatty acids in both pregnant females and embryos. Significant differences were found among eggs, embryos and pregnant females for all fatty acids groups with the exception of saturated fatty acids for embryos and pregnant females. The principal components analysis revealed that embryos are particularly related to n-6 PUFA and pregnant females with n-3 PUFA. A close relationship exists between the Hg level of pregnant females and the Hg level of their embryos which indicates that there is a transfer of mercury from maternal sources. The comparison of the mean dry weight between eggs and embryos showed a gain of 3.8% obtained in the embryos. Histological sections of the uteri of pregnant females showed a high level of both superficial and inner vascularization in the uterine villi as well as the presence of secretor cells. Until now, the importance of this species maternal contribution and interference for the embryos development has never been documented. However, the biological and chemical results observed in the present work show that there is a matrotrophic strategy for the birdbeak dogfish.

Deep-water fishing tactics of the Spanish fleet in the Northeast Atlantic. Seasonal and spatial distribution

The classification and identification of all the Spanish fishing activity targeting deep-sea species was conducted using a non-hierarchical classification technique designed for large matrices (CLARA). Otter trawl and set longlines were the main gears used in deep-sea ecosystems. The otter trawl fleet conducted 3 deep-sea fishing tactics. The only otter trawl fishing tactic targeting deep-sea species was that working in the VI ICES Division and targeting Alepocephalus baiirdi . The other 2 otter trawl fishing tactics targeted shallower shelf demersal resources, deep-sea species being secondary ( Phycis blennoides ). The longline fleet carried out 7 fishing tactics targeting deep-sea species ( Molva spp.; deep water sharks; P. blennoides; Pagellus bogaraveo ; and Trichiuridae) and 2 fishing tactics targeting Conger conger , which perform as deep-sea fishing tactics in the narrow continental shelf area. This classification, together with knowledge regarding their seasonal performance and spatial distribution, may help to design fisheries sampling protocols and to improve the management of these fleets, thus reducing their impact on deep-sea habitats.

Sperm storage in males and females of the deepwater shark Portuguese dogfish with notes on oviducal gland microscopic organization

Sperm storage in males and females was studied for the deepwater shark Portuguese dogfish Centroscymnus coelolepis. In males, sperm is stored in the seminal vesicle from early maturity stages until mating. The epithelium of the seminal vesicle secretes an acid mucopolysaccharide that might preserve sperm until it is released. The oviducal gland (OG) presents the four distinct zones described for other elasmobranchs: club, papillary, baffle and terminal. Mature, pregnant, resting and regenerating females are able to store sperm in the terminal zone. Sperm was found within sperm storage tubules (SSTs), involved by a secretory matrix. The localization of SSTs deeper in the OG suggests long-term sperm storage, which is in agreement with the long reproductive cycle described for this species. Sperm storage is an advantage for this deepwater species that presents sexual segregation and lives in a food-constrained environment, increasing the efficiency in reproduction.

Age, growth and reproduction of a common deep-water shark, shortspine spurdog (Squalus cf. mitsukurii), from Hawaiian waters

About half of the extant shark species occur only in deep waters (defined as >200 m depth), yet few published studies on sharks include these taxa. As fisheries worldwide enter deeper waters, the provision of biological data for these little-known taxa is critical to management and conservation. The shortspine spurdog, Squalus cf. mitsukurii, is an abundant shark on the insular slopes of the Hawaiian Islands. We assigned ages by counting growth bands on the enamel caps of both dorsal fin spines. Age estimates ranged from 3 to 26 years for females and from 6 to 23 years for males. Growth was modelled with multiple length-at-age models, fitted using maximum likelihood estimation and nonlinear least-squares methods. For female data, the logistic model yielded the most biologically cogent parameter estimates (L∞ = 126 cm (total length, TL) and k = 0.080 year–1). The two-parameter von Bertalanffy Growth Model yielded optimal model fit and realistic parameter estimates for males (L∞ = 72 cm (TL) and k = 0.080 year–1). Maturity ogives suggested that females and males mature at 64-cm TL (15 years) and 47-cm TL (8.5 years), respectively. Fecundity ranged from 3 to 10 embryos; mating appeared to be aseasonal. We reveal a conservative life history, common among deep-water elasmobranchs, and provide further evidence of geographic variation in reproductive and growth parameters in this nominal species.

Effects of deep-sea bottom longlining on the Hatton Bank fish communities and benthic ecosystem, north-east Atlantic

The effects of deep-sea bottom longlining on fish communities and the benthic ecosystem, as well as the interactions between fishing and seabirds, were studied based on data collected from a joint collaboration between the Spanish Institute of Oceanography and a longliner, carried out on the Hatton Bank area (north-east Atlantic) in 2008. A total of 38 longline sets were distributed mainly along the rugged bottom of the rocky outcrop at depths ranging from 750 to 1500 m. Deep-water sharks and lotids were predominant in the catches contributing respectively 80.4% and 13.1% in terms of weight. Deep-water sharks were predominant in the discards. By-catch of cold-water corals and small glass sponges occurred along the western flank of the Hatton Bank, while large hexactinellids were found along the eastern flank. Longlines fished the adult fraction of vulnerable deep-water sharks and lotids. High catches per unit effort values for these species were obtained in coral areas. A combination of seabird-scaring streamer lines and other measures of preventing seabird by-catch were used. Only one fulmar was captured and it survived. Data on distribution of marine litter and derelict deep-sea gillnets are also presented.

Identification of métiers of the Spanish set-longline fleet operating in non-Spanish European waters

The Spanish set-longline fleet operating in ICES Subareas VI, VII and Divisions VIIIabd is composed of two fleet segments distinguished according to tonnage: vessels larger and shorter than 100 grt. Spanish regulations allow Spanish-registered longliners fishing in European waters to prosecute three different types of fisheries, namely targeting hake, targeting non-TAC species and targeting deepwater species. Due to the fact that the type of license is not registered in logbooks, together with the recent changes in the regulation of fishing on some non-TAC and deepwater species, conducting multivariate analyses of landing profiles at species level becomes the most appropriate way to identify fisheries and métiers. A 3-step approach was used, consisting of clustering of landings profiles (2004–2006), interviews with skippers by group, and an exploration of the spatial–temporal patterns in both sources of information. The results obtained allowed us to identify eight fisheries. Of these, four fisheries were common to both fleet segment giving eight métiers: directed at hake, forkbeards, lings, and conger. Of the remaining four métiers, the mixed métier developed by vessels shorter than 100 grt occurred throughout the period studied, while the remaining three métiers showed discontinuous patterns and were directed at bluemouth, Atlantic pomfret, and deepwater sharks, respectively. The two first métiers appeared in 2006, while the last one was found to occur during 2004–2005 but disappeared in 2006. The obtained results allow us to match the Spanish fishing license system with the métiers classification used by the Common DCF (data collection framework) taking into account the current categorization of species in regulations.

Size at maturity and length-weight relationships of the blurred lantern shark Etmopterus bigelowi (Squaliformes: Etmopteridae) caught off southeastern Brazil

The blurred lantern shark Etmopterus bigelowi, a deep-water squaloid shark, is globally widespread in temperate and tropical waters, but there is little available information about its biology owing to its relative rarity of capture and taxonomic confusion with its sibling species Etmopterus pusillus. Specimens used in this study were collected from July to December 2004 as by-catch in the commercial deepwater trawl fishery targeting red shrimp Aristaeomorpha foliacea in the southwestern Atlantic. We examined 55 specimens (22 males and 33 females) ranging in total length (TL) from 31.5 to 73 cm and in total weight from 103 to 1600 g. Length-weight relationships were explored for each sex and significant differences were found in the slope coefficients of the male and female regressions. The size at maturity for each sex was evaluated fitting a logistic regression. Females matured at larger sizes than males, with estimated sizes at first maturity of 56.0 cm TL for females and 45.1 cm TL for males. The present study provides important preliminary information about E. bigelowi that can be incorporated in risk assessment and stock assessment models, essential for efficient management practices aimed at avoiding overexploitation of these vulnerable deep-sea sharks.

Depth distribution of the velvet belly, Etmopterus spinax, in relation to growth and reproductive cycle: The case study of a deep-water lantern shark with a wide-ranging critical habitat

The velvet belly lantern shark, Etmopterus spinax (Squaliformes: Etmopteridae), is a small-sized squalid shark commonly found in deep waters off the Portuguese coast, mainly on soft bottoms. In this study, 67 research cruise bottom trawl tows (with 1-hour duration) were carried out at depths that ranged from 84 to 786 m. A total of 396 specimens (192 males and 204 females) were caught, with total lengths and ages ranging, respectively, from 10.2 to 32.9 cm and 0 to 7 years for males and from 9.8 to 41.1 cm and 0 to 10 years for females. Size, age, sex and maturity stages were found to be correlated with depth, with the larger, older and mostly mature specimens occurring predominantly at greater depths. There seems to be a depth-related migration, where the pregnant females migrate from deeper mating grounds to shallower nursery grounds. The sex ratios were relatively similar in the shallower strata, but females dominated at more than 600 m and were exclusive at more than 700 m. Fishing-related mortality may have complex and significant repercussions on this species, given that commercial fisheries are impacting different segments of this population differently.

Comparing Atlantic and Mediterranean populations of the velvet belly lanternshark, Etmopterus spinax, with comments on the efficiency of density-dependent compensatory mechanisms

Etmopterus spinax is a small-sized deep-water lantern shark that occurs in the Eastern Atlantic and the Mediterranean. Differences in depth distribution, densities, size at maturity and fecundity were compared between a population that has suffered high levels of fishing mortality during the last decades (Southern Portugal in the northeast Atlantic) and a population where low fishing pressure below 500 m occurs at present or has occurred in the last decades (Northern Alboran Sea in the western Mediterranean). The density of this species, as derived by experimental bottom trawl survey, off the coast of Southern Portugal, is substantially lower than in the Northern Alboran Sea throughout the entire depth range. The Atlantic population is maturing at smaller sizes than the Mediterranean population and has a lower mean fecundity. Specifically, sizes at maturity for Southern Portugal and the Northern Alboran Sea were, respectively, 25.39 and 28.31 cm TL for males and 30.86 and 34.18 cm TL for females, while mean fecundities for Southern Portugal and the Northern Alboran Sea were, respectively, 9.94 and 11.06 oocytes per mature female. This work demonstrated the possible presence of density-dependent mechanisms in the Southern Portuguese population of E. spinax that has lowered the size at maturity as a possible result of excessive fishing mortality. However, given that this is an aplacentary viviparous shark, where fecundity is dependent on female size, this compensatory mechanism seems to have a limited efficiency.

The diet of deepwater sharks and the benefits of using DNA identification of prey

Stomachs from the sharks Dalatias licha, Centrophorus squamosus, Centroscymnus owstoni, Centroselachus crepidater, Proscymnodon plunketi, and Galeorhinus galeus were sampled from three research trawl surveys on Chatham Rise, east of New Zealand. Between 14 and 50 stomachs were examined for each species, of which 8–62% were empty. Prey were visually identified in 80 stomachs, and by DNA barcoding in a further 28 stomachs. The use of DNA methods allowed the identification of chunks of flesh found in the stomachs of D. licha and P. plunketi, and nearly doubled the rate of data accumulation for D. licha, C. squamosus, and C. owstoni. Between 84 and 223 stomachs were estimated to be needed to measure 90% of the extrapolated total prey richness. The prey of D. licha, C. squamosus, and P. plunketi were predominantly benthic or demersal fishes and cephalopods. The prey of C. owstoni and C. crepidater were predominantly mesopelagic fishes and squids. G. galeus foraged throughout the water column. Scavenging of discards from commercial fishing vessels was likely in C. squamosus, P. plunketi, and G. galeus. The diet of all species except C. crepidater was dominated by the commercially important benthopelagic species hoki Macruronus novaezelandiae.

Effects of deep-water coral banks on the abundance and size structure of the megafauna in the Mediterranean Sea

Abstract The Santa Maria di Leuca (SML) coral banks represent a rare example of living Lophelia-Madrepora -bearing coral mounds in the Mediterranean Sea. They are located between 350 and 1100 m in depth, in the northern Ionian Sea (eastern-central Mediterranean). Using a multi-beam echo sounder, side-scan sonar, high-resolution seismics and underwater video, the zones were identified for the sampling demersal fauna without damaging the coral colonies. During September–October 2005 experimental samplings were carried out with longlines and trawl nets inside the coral habitat and outside, where fishery exploitation occurs. No significant differences were shown between the abundance of fish recorded using longlines in the coral and non-coral habitat even though some selachians and teleosts were more abundant in the former than in the latter. Large specimens of rockfish ( Helicolenus dactylopterus ) and blackspot seabream ( Pagellus bogaraveo ) were commonly caught using longlines in the coral habitat. Data from trawling revealed refuge effects in the coral habitat and fishing effects outside. Significant differences were detected between the recorded abundances in the two study areas. Greater densities and biomasses were obtained inside the coral area, and fish size spectra and size distributions indicate a greater abundance of large fish inside the coral habitat. The SML coral habitat is a spawning area for H. dactylopterus . The remarkable density of the young-of-the-year of the deep-water shark Etmopterus spinax as well as of Merluccius merluccius , Micromesistius poutassou , Phycis blennoides and H. dactylopterus , indicates that the coral habitat also acts as nursery area for these demersal species, which are exploited outside. Considering the evidence of the negative impact of bottom trawling and, to a lesser extent, of longlining, the coral banks can provide a refuge for the conservation of unique species and habitats as well as in providing benefit to adjacent fisheries through the spill-over effect both of eggs, larvae, juveniles and adults.

First approach to the biology of the deep-water shark Deania profundorum (Chondrichthyes: Centrophoridae)

This is the first work describing some biological aspects of the arrowhead dogfish, Deania profundorum . The specimens were captured in two surveys (2004–2005) between 151 and 1200 m off the Madeira archipelago (north-east Atlantic Ocean). A total of 351 females (36–110 cm) and 169 males (27–94 cm) were sampled. The smallest (27 cm) and the biggest (110 cm) specimens ever caught were recorded. Females were most abundant in the overall depths, apart from the middle range of 451–1050 m where the sex-ratio was 1:1. A vertical stratification by size occurred, since all the juveniles less than 40 cm length were caught deeper than 950 m. This species was sexually dimorphic with females growing to larger sizes than males and being larger at first maturity. All stages of maturity were found during the sampling period. Nineteen gravid females with six to 11 embryos (9–18 cm length) were found. The data obtained indicate that the Madeira slopes are a nursery and reproductive area for D. profundorum .

Lost and abandoned nets in deep-water gillnet fisheries in the Northeast Atlantic: retrieval exercises and outcomes

Abstract Large, P. A., Graham, N. G., Hareide, N-R., Misund, R., Rihan, D. J., Mulligan, M. C., Randall, P. J., Peach, D. J., McMullen, P. H., and Harlay, X. 2009. Lost and abandoned nets in deep-water gillnet fisheries in the Northeast Atlantic: retrieval exercises and outcomes. – ICES Journal of Marine Science, 66: 323–333. The methods used and the results, including estimates of ghost catches present at the time of retrieval, from Irish and UK (England and Wales) gillnet retrieval exercises carried out in deep-water gillnet fisheries west of the British Isles are described. Summaries of the exercises are currently found only in the grey literature, and there is a need to make them more widely available to the scientific community. The fisheries are currently principally for anglerfish (mainly Lophius piscatorius), along with a small bycatch of deep-water sharks [mainly leafscale gulper shark (Centrophorous squamosus) and Portuguese dogfish (Centroscymnus coelolepis)]. The methods used and the results from retrieval exercises in the Norwegian Greenland halibut (Reinhardtius hippoglossus) gillnet fishery are also presented. It is suggested that the efficiency of the Norwegian retrieval gear (which was used in all but one of the retrieval exercises described) be investigated under a range of conditions using an attached underwater camera. The outcomes from this could be used to improve the design of retrieval gear and future gillnet retrieval survey/mitigation exercises. Suggestions are made to improve the format and interpretation of results from future retrieval surveys and to enhance their value to fishery managers and stock assessment scientists. The importance of the continued need for structured gillnet retrieval exercises in deep-water gillnet fisheries is emphasized, and suggestions are made for conducting future studies.