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Average depth distribution by sex, maturity, and size for snow crab on the Grand Bank (Divisions 3LNO) during spring from 1996-2015.
Contexts in source publication
Context 1
... fishery targets deep portions of the continental shelves where large males are common. Crabs undertake ontogenetic migrations from shallow areas in early life toward deeper areas as they age (Figure 7). The down-slope movement toward deep water is associated with warmer temperatures at increased depth, with more molts undertaken and larger sizes achieved before terminal molt in warm water. ...
Context 2
... from the Grand Bank, the biggest and most productive area of snow crab distribution in NL, suggest a similar scenario. There, largest adult males appear spatially segregated from largest females during spring while the depth distribution of largest adolescent males is more closely associated with largest breeding females at greater depths of about 250-300 m ( Figure 7). Although mating dynamics are not fully understood, the segregation of largest adult males from largest breeding females suggests that the small portion of the population targeted by the fishery may not be critically important to reproductive capacity. ...
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Precautionary Approach framework for Newfoundland and Labrador Snow Crab
Citations
... Whether this result was due to a great abundance of undersized crabs in the area and/or the lack of size selection in the pots was unknown. However, the mesh size used was smaller than that recommended in previous studies [38,39], which may have contributed to the retention of many undersized crabs. Researchers have reported that pots need at least 14 days for all undersized snow crabs (< 100 mm carapace length) to exit the pot to reach 100% size selection at the seabed [38,39]. ...
... However, the mesh size used was smaller than that recommended in previous studies [38,39], which may have contributed to the retention of many undersized crabs. Researchers have reported that pots need at least 14 days for all undersized snow crabs (< 100 mm carapace length) to exit the pot to reach 100% size selection at the seabed [38,39]. Although soaking time varied between 5 and 16 days in our study and may have affected size selection, it was not accounted for in the analysis because it equally affected both the test and the standard pots being paired in the individual sets. ...
The snow crab (Chioneocetes opilio) fishery in the Barents Sea is carried out by large offshore vessels, as the fishing grounds are located far from shore and the gear must be transported back and forth over long distances. Therefore, fishers use stackable conical pots that allow large numbers of pots to be carried on deck for each trip. One of the drawbacks of using stackable pots is that the entrance is at the vertex of the conical pot, which fishers claim does not provide the desired fishing efficiency. Thus, the goal of this study was to determine whether a different pot design would improve the catch efficiency of snow crabs. We investigated the efficiency of a new type of pot called the moon pot, which provides continuous increased bait odour intensity as snow crabs make their way towards the entrance of the pot. This alteration was expected to increase catch efficiency compared to that of the conical pots used by the fleet today. However, experimental fishing results showed that the modified pots had significantly lower catch efficiency than the standard conical pots, as only ~66% of the number of crabs caught by the conical pots were caught in the moon pots. The main reason for this reduced catch efficiency likely was the initial steepness of the moon pot, which may have made it difficult for crabs to reach the pot entrance. These results demonstrated that pot design can dramatically affect catch efficiency of snow crabs.
... Snow crab (Chionoecetes opilio) is a commercially important species on the east coast of Canada, in particular the provinces of Quebec, New Brunswick, Nova Scotia, and Newfoundland and Labrador (Dawe & Mullowney, 2016;DFO, 2016;Hébert, Miron, Moriyasu, Vienneau, & DeGrâce, 2001). This fishery has been the world's largest snow crab fishery for the last few decades, with total landings of 93,519 mt annually (Dawe & Mullowney, 2016;DFO, 2015). ...
... Snow crab (Chionoecetes opilio) is a commercially important species on the east coast of Canada, in particular the provinces of Quebec, New Brunswick, Nova Scotia, and Newfoundland and Labrador (Dawe & Mullowney, 2016;DFO, 2016;Hébert, Miron, Moriyasu, Vienneau, & DeGrâce, 2001). This fishery has been the world's largest snow crab fishery for the last few decades, with total landings of 93,519 mt annually (Dawe & Mullowney, 2016;DFO, 2015). This fishery targets only adult male crabs with a minimum landing size of 95 mm carapace width (CW). ...
... In Newfoundland and Labrador, the commercial fishery for snow crab began in the 1960s (Dawe & Mullowney, 2016). Annual landings were initially low, but dramatically increased from approximately 10,000 mt in 1970 to 69,000 mt in 1999 (Dawe & Mullowney, 2016;DFO, 2016). ...
This study investigated the effect of installing underwater light-emitting diode (LED) lights in different locations (close and distant to the trap entrance) and orientations (normal and upside down direction) inside baited traps targeting snow crab (Chionoecetes opilio) off the coast of Newfoundland and Labrador, Canada. Four experimental treatments were evaluated in comparison with traditional baited traps (control). Our results showed each of the experimental treatments produced significantly higher (39%-57%; 48% on average) catch per unit effort (CPUE) compared to the control traps, with no significant differences for both legal and sublegal-sized crab among the different experimental treatments. Longer soak times significantly increased the CPUE of the illuminated traps, but did not affect the catch rate of the control traps. Our results also indicated crab size frequency distributions were independent of experiment treatments. Our results suggest that fishing enterprises could improve their catching performance by adding LED lights to their traps, but the location and orientation of the lights appears unimportant.
... The Newfoundland and Labrador snow crab fishery had a slow beginning in the 1960s, but grew to become the largest snow crab fishery in the world during the past two decades, while maintaining Marine Stewardship Council certification since 2013 (MSC, 2013;Dawe and Mullowney, 2016). The Crab Management Areas (CMA) have no biological relevance, and the resource status is managed by larger units based on the Northwest Atlantic Fisheries Organization (NAFO) Divisions, with inshore and offshore regions considered separately (Figure 1.2). ...
... This small-scale inshore fishery remained stable until the early 1990s when significant expansion began. Following the collapse of many groundfish stocks during the early 1990s, the snow crab fishery quickly became the most important in terms of social and economic value (Dawe and Mullowney, 2016;Mullowney et al., 2018). The crab fishery continued to expand in Newfoundland and Labrador during the 1990s as a result of growing Japanese market demand and industry diversification (Mullowney et al., 2018). ...
... The fishery excludes females (DFO, 2018a). Females, undersized males, and uncaught legal sized males are assumed to be sufficient to maintain the reproductive potential of the resource Dawe and Mullowney, 2016). Under-sized and soft-shelled males that are retained in the traps must be returned to the sea (DFO, 2018a). ...
Snow crab (Chionoecetes opilio) is an important commercial shellfish and one of the most valuable fisheries in eastern Canada. The Newfoundland and Labrador snow crab fishery has been the world’s largest for the past two decades. Total landings grew substantially between the 1980s and 1990s, but more recently, the industry has been faced with new challenges including decreases in stock abundance (i.e., poor pre-recruitment), changes in environmental condition (i.e., warming ocean water temperatures), conflicts with shrimp trawlers, effects of seismic exploration, and increases in operating costs. Maintaining the economic viability of small fishing businesses in the presence of these new stressors can be a challenge. In output-controlled fisheries such as snow crab, improving the catch rate of existing traps is an effective method of improving the financial viability of small fishing businesses. In this thesis, I conducted a comprehensive examination of the behaviour of snow crab in response to artificial light (i.e., Light-Emitting Diode (LED) lights and luminescent netting), including laboratory and field experiments, to address the primary goal of improving the catch rate of small conical traps commonly used for catching snow crab in the North Atlantic Ocean.
First, I conducted a literature review regarding the use of artificial light in a commercial industrialized fisheries. The review provides valuable knowledge and reference for scientists, managers, and fishermen on animal behaviour in response to artificial light. It also addresses the trade-off between positive effects such as increased catch rate and reduced bycatch with negative effects such as the production of increased plastic, ocean litter, and greenhouse gas emission. Second, I conducted 7 experiments to investigate the behaviour of snow crab in response to artificial light, including 2 laboratory studies and 5 field studies, to address the primary goal of improving the catch rates of snow crab traps. Results from the laboratory experiments indicated that snow crabs responded differently to different light colours. Field experiments in 2016 demonstrated that equipping baited traps with small low-powered LED lights increased the Catch Per Unit Effort (CPUE; number of crabs per pot) of the traps (i.e., 77% and 47% for white and purple LED lights, respectively). Next, I examined the effect of installing underwater LED lights in different locations and orientations inside baited traps targeting snow crab off the coast of Newfoundland and Labrador, Canada. Results from this field experiment in 2017 revealed that the location and orientation of lights does not appear to be important. Next, I conducted a comparative fishing study onboard a large offshore fishing vessel targeting snow crab in the Barents Sea, off the coast of Norway. Results revealed that equipping baited traps with purple lights increased the CPUE by 11.6%, although the results varied with the density of crab.
Finally, I examined the potential application of luminescent netting as a source of artificial light to determine whether it could be used to improve the CPUE of traps. A benchtop laboratory experiment was conducted to measure the duration of luminescence using time-lapse photography. I found that luminescent netting can be activated to emit light and that the resulting intensity and duration of luminescence emitted over time, depends on the initial duration of UV exposure and the source of light. A follow-up field experiment in 2018 showed that luminescent traps significantly increased the catch rate of snow crab compared to traditional traps.
Overall, the results of my PhD research demonstrate that artificial light can improve the catch rates of snow crab traps, with examples from different light sources (i.e., LED light, luminescent netting) and locations (Barents Sea, Newfoundland and Labrador). These results suggest that the application of artificial light in commercial snow crab fisheries could improve the financial viability of fishing enterprises.
... To date, the WG has not established a proposal satisfactory enough to proceed with implementation of a formal framework. The WG has advocated that the confluence of unique biological attributes of Snow Crab, a high level of climate regulation of the resource (Mullowney et al. 2014), and a stringent set of management regulations already constitutes a sufficient PA/DM framework for this fishery (Dawe and Mullowney 2016). A major point the WG has advanced is that the exploitable biomass of male Snow Crab (≥95 mm carapace width [CW]), the portion of the resource targeted by the fishery, is not an appropriate analog for SSB (or a similar measure of stock status) in a framework. ...
... Under historic and current management practices, prolonged serious or irreversable harm has never knowingly been inflicted upon the resource through fishing. Above all else, the large-mesh traps used in the fishery constitute a precautionary management measure (Dawe and Mullowney 2016). However, under the current regime there remains potential for serious biological harm through fishing to occur as there is no explicitly identified upper limit(s) on harvest rates. ...
Precautionary Approach framework for Newfoundland and Labrador Snow Crab
... A Total Allowable Catch (TAC) and quota allocation management system was applied by the late 1980s (DFO, 2016a). Since 1973, regulating the minimum legal landing size to >95 mm carapace width (CW) and excluding the capture of females has provided an effective precautionary approach to fisheries management (Conan & Comeau, 1986;Dawe & Mullowney, 2016). By the early 1990s, snow crab had become a very important commercial fishery and a major economic contributor to Canada's most eastern province. ...
This study investigated the behaviour and commercial catchability of snow crab (Chionoecetes opilio) in response to different low-powered LED lights under laboratory and field conditions. We created a novel choice-experiment in a laboratory setting in which we investigated the behaviour of snow crab in response to coloured LED lights. The results showed that snow crab movement was dependent on light colour, with animals choosing to move toward blue and white lights, away from purple lights, and no detectable effect for green and red lights. We then conducted two field experiments to investigate the effect of the same LED lights on the catch rates of commercial traps during the 2016 snow crab fishery on the east coast of Newfoundland and Labrador. Results from the first field experiment showed that adding white and purple LED lights into baited traps significantly improved Catch Per Unit Effort (CPUE) by 77% and 47% respectively. Results from the second field experiment showed that unbaited traps equipped with only LED lights (no bait), could also catch snow crab in comparable amounts to traditional baited traps, with soak time and depth explaining some of the variation in CPUE. Taken together, these experiments suggest that fishing enterprises can improve their catching performance and profitability by adding LED lights to their traps, or by using LED lights as a bait replacement.
The southern king crab Lithodes santolla is a commercially very valuable decapod of the family Lithodidae. Although it is widely distributed on the Argentinian continental shelf, individuals are mainly grouped into a few sectors. The most productive argentine king crab fishery in the country has been developed since 2004 on the Patagonian Central Sector (PCS), which comprises the San Jorge Gulf and the continental shelf region between 44º and 48 ° S. In the present study the evolution of catches and fishing effort are investigated, abundance indices are estimated, and the spatial distribution, the population structure, and the main events of the king crab life cycle are characterized, based on data collected by scientific observers onboard the crab commercial fleet and those obtained during research surveys.
From the beginning of the fishery, the management has been based on the so-called “3S principle” (size, sex, and season). Only males above 110 mm can be landed during the fishing season, and the definition of such a season was modified as the knowledge about the life cycle increased over time. The exclusive use of traps to catch this species and the full coverage of the fleet by observer program agents were also established, essential to properly monitor and assess this commercial activity. In fact, between October 2004 and June 2016, direct records were obtained on 85% of the fishing hauls, making this marine fishery one with the highest coverage in the country.
Until the 2009-2010 season, the only licensed crabber vessel landed an average of 700 tons, whereas during the period 2010-2011 to 2015-2016 since four vessels were authorized and catches increased until reaching a peak of 3,700 tons. Null catches were very scarce, demonstrating the efficiency of the traps to catch these crustaceans. As a result of changes that occurred over time in the number of authorized vessels, new jurisdictions opened to fishing, and resource abundance, variations in the spatial distribution of fishing effort were verified. It was mainly concentrated on the Southern Sector of the shelf (46º-48º S), but the North Sector (44º-46º S) and Chubut within the San Jorge Gulf, were important fishing grounds during the last period. Abundance indices on both Total Catch and Legal-sized Males were estimated from fishing data using a General Linear Model (GLM). Declining trends in the indices along the last four fishing seasons were determined, and a drop of 28% for the legal males was found. Considering the spatial dispersion of the fishery since the 2011-2012 season, these indices seemed to properly reflect the actual variations in population abundance.
In order to understand the population dynamics of this species, different aspects of its live cycle were studied. The catch retained in the traps was characterized by a predominance of males, although in recent seasons a decreasing trend in the proportion of specimens of this sex, mainly those of commercial legal size, and a reduction in the average carapace length were observed. These changes are possibly associated with the selective nature of this fishing. The sex ratio varies during a fishing season, because the catchability decreases during the carapace molt, therefore the proportion of mature females is lower in November-December, while those of males decreases in autumn. The mandatory use of three escape rings in the trap since the 2014-2015 season markedly reduced the capture of females and non-legal males. An estimate of the carapace length at which 50% of individuals are retained by these traps (LC50%) was performed. In addition, the proportions of mature, non-ovigerous females, as an indicator of the lack of available male mates, were analyzed and the length of the first maturity was estimated. The temporal variability associated with the beginning of both the molting and mating processes was considered to be negligible. The carapace wear and the color of the ventral surface of the carapace were used to determine the aging of the carapace and to describe the inter-molt period.
The crab spatial distribution covered nearly all the Patagonian Central Sector, and it was characterized by stable aggregations over time. During systematic research surveys using traps, the highest densities of males were identified on the San Jorge Gulf, mainly within Santa Cruz jurisdiction, and also two other important aggregations were located on the shelf to the north and south 46ºS parallel. These results were consistent with the estimated abundance indices, and the areas where fishing effort is concentrated, as well as where king crab catches occurred during the trawl surveys to evaluate shrimp and hake carried out. A possibly linking, transitional zone showing very low abundances were identified among the above-mentioned shelf aggregations. The size distribution of both sexes was similar and remained stable. The average sizes increased towards the central region of the San Jorge Gulf and towards the east on the shelf. The evaluation surveys carried out with fishing vessels allowed to obtain highly accurate data over a short period of time.
The first data on southern king crab in the PCS came from research surveys targeting hake and prawn by using trawling nets. The hake surveys covered the period 1997-2014 and a wide sector. On the other hand, five shrimp cruises including an area of interest for southern king crab studies which was restricted to the San Jorge Gulf were selected. The presence of southern king crab increased over the years due to a gradual expansion on the shelf. The 8ºC and 10ºC isolines generally delimited the sectors where maximal catches were taken, whereas they were scarce or even null between Camarones and Rawson, where bottom temperatures exceed 11ºC in summer. The estimated densities in both of the mentioned surveys were consistent, having a maximum in 2011, without correlation in the following years, for this reason, this event would be associated with changes in catchability.
The increase in southern king catches determined the appearance of the first signs of overexploitation, such as the reduction in the abundance indices over the main fishing sectors, and decreases in both the proportion of males as well as their average length. In order to monitor the fishery, four population indicators are proposed to be annually analyzed: percentage of males, the average carapace length of males, the percentage of non-ovigerous mature females (≥ 70 mm), and the percentage of females having a full clutch. This work provides a baseline analysis on key biological-fishing issues aspects of southern king crab in PCS, which were studied since the very beginning of targeted fishing of this species, with the aim of achieving sustainable exploitation and adaptive ecosystem management.
