Snow Crab Fishery Research Articles

Using hidden Markov models to infer vessel activities in the snow crab (Chionoecetes opilio) fixed gear fishery and their application to catch standardization

Tracking vessel movements has become increasingly important in fisheries research to identify fishing grounds, monitor responses to area closures, and other actions for fishery managers. Vessel monitoring systems (VMS) have given fishery managers and researchers the ability to study vessel interactions by automated tracking of vessels throughout fishing seasons. The high spatial and temporal resolution obtained from VMS records in the Gulf of St. Lawrence snow crab (Chionoecetes opilio) fishery provides information on movement patterns and fishing locations. With the use of hidden Markov models (HMM), we inferred behaviours exhibited by the fishermen during the course of fishing trips and related these behaviours to catch rates across years with varying abundance estimates. The HMM classified three behavioural states in the VMS data that were identified with travelling, setting traps in novel locations (new sets), and retrieving previously set traps (resets). Catches within a trip were modeled by combining VMS-based estimates of these behaviours with logbook information in a generalized linear model. Our model demonstrates that behavioural variables can contribute to the standardization of catch similar to classical trip and vessel variables used in constructing abundance indices.

Evaluating potential biodegradable twines for use in the snow crab fishery off Newfoundland and Labrador

Several technological advancements exist for the purpose of disabling baited traps if they are lost or abandoned at sea. In this study, we investigated various biodegradable twines for their potential use in the snow crab (Chionoecetes opilio) fishery off Newfoundland and Labrador, Canada. The twines were deployed at sea for a duration of 124 days to measure degradation in breaking strength (kgf) over time. Results revealed significant variation in degradation rates among the twine types tested. Among the best performing twines, was the 3-ply cotton 96-thread twine. This twine exhibited a rapid and noticeable decline in breaking strength over the period of study with a total reduction of 63% of the initial strength upon conclusion of the study. This particular twine is now a mandatory condition of licence for all fishing enterprises targeting snow crab in the province of Newfoundland and Labrador.

Cooperative Formation and Peer Effects in Fisheries

ABSTRACT The economic benefits that arise following the transition to a rights-based fishery management regime accrue on both the extensive and intensive margins. This research explores the changes in fleet composition, economic performance, and coordination that occurred following the introduction of the Bering Sea Crab Rationalization Program. On the extensive margin, we estimate the relative efficiency of vessels within each fishing cooperative to look for potential arbitrage opportunities when selecting which vessels will fish the cooperative's quota allocation. On the intensive margin, we investigate the role of peer effects in facilitating the flow of information within the cooperative. The results support two hypotheses within the red king and snow crab fisheries: (1) the cooperatives which formed appear to have exploited the intracooperative efficiency arbitrage opportunities, and (2) an increase in landings by a fellow cooperative member tends to increase one's own landings, a positive peer effec...

Potential for bowhead whale entanglement in cod and crab pot gear in the Bering Sea

AbstractBowhead whales (Balaena mysticetus) of the western Arctic stock winter in ice‐covered continental shelf regions of the Bering Sea, where pot fisheries for crabs (Paralithodes and Chionoecetes spp.) and Pacific cod (Gadus macrocephalus) pose a risk of entanglement. In the winter of 2008–2009 and 2009–2010 the spatial distribution of 21 satellite tagged bowhead whales partially overlapped areas in which pot fisheries for cod and blue king crab (Paralithodes platypus) occurred. However, these fisheries ended before whales entered the fishing areas, thus avoiding temporal overlap. A fishery for snow crab (Chionoecetes opilio) typically runs from January to May and provides the greatest potential for bowhead whales to encounter active pot gear. Tagged whales did not enter the area of the snow crab fishery during this study and generally remained in areas with >90% sea ice concentration, which is too concentrated for crab boats to penetrate. Pack ice sometimes overruns active fishing areas, resulting in lost gear, which is the most likely source of entanglement. The western Arctic stock of bowhead whales was increasing as of 2004; as such, incidental mortality from commercial pot fisheries is probably negligible at this time. Regardless, entanglement may increase over time and should be monitored.

Growth per Molt of Snow Crab in the Eastern Bering Sea

AbstractThe growth per molt of snow crab Chionoecetes opilio in the eastern Bering Sea is poorly known, primarily because snow crabs are difficult to sample during their spring molting period due to the presence of sea ice. To provide better estimates of growth per molt for the stock assessment model used to manage the snow crab fishery, a study was conducted to collect juvenile crabs with a bottom trawler and return them to holding facilities at Dutch Harbor and Kodiak, Alaska. Since relatively few of these crabs subsequently molted, these data were augmented with molting data collected by two previous, unpublished studies. Based on a total of 35 observations, snow crabs grew according to the following premolt (PRMW) and postmolt (POMW) carapace width relationships: POMW = −4.00 + 1.46(PRMW), where PRMW < 36.1 mm, and POMW = 48.83 + 1.17(PRMW − 36.1), where PRMW ≥ 36.1 mm.Received July 23, 2012; accepted September 13, 2012

Fisheries management for regime-based ecosystems: a management strategy evaluation for the snow crab fishery in the eastern Bering Sea

Abstract Szuwalski, C., and Punt A. E. 2013. Fisheries management for regime-based ecosystems: a management strategy evaluation for the snow crab fishery in the eastern Bering Sea. – ICES Journal of Marine Science, 70: 955–967. Regime shifts are a prominent feature of the physical environment of some ecosystems and have the potential to influence stock productivity. However, few management strategies or harvest control rules (HCRs) consider the possibility of changes in stock productivity. A management strategy evaluation is conducted for the snow crab (Chionoecetes opilio) fishery in the eastern Bering Sea, an ecosystem influenced by regime shifts. Operating models that project recruitment as a single average (i.e. the current basis for management advice), regime-based with no relationship between recruitment and spawning biomass, and regime-based with control of recruitment oscillating between environmental conditions and spawning biomass are considered. An HCR that accounts for shifts in recruitment regime is compared with the status quo HCR for each operating model. The regime-based HCR increases yield and decreases variability in yield at the cost of a higher probability of overfishing in regime-based systems. However, the regime-based HCR slightly decreases yield (no change in variability) and increases the probability of overfishing in non-regime-based systems. Identifying changes in productivity that are definitely driven by environmental regime rather than fishing pressure is the largest difficulty in implementing these rules.

Managing harvest risk with catch-pooling cooperatives

Abstract Sethi, S. A., Dalton, M., and Hilborn, R. 2012. Managing harvest risk with catch-pooling cooperatives – ICES Journal of Marine Science, 69: 1038–1044. Catch-pooling cooperatives are a strategy for fishers to manage variability which can be organized independently of a central management agency. We examined the statistical properties of equal-share catch-pooling cooperatives, and tested their potential to mitigate risk using data from two Bering Sea crab fisheries prior to rationalization. The results suggest that small cooperatives of crabbers could have reduced vessel-level catch risk by as much as 40% in the red king crab fishery, but would have been ineffective in the snow crab fishery. Analytical examination of catch variances under cooperatives explains the discrepancy between the two fisheries and demonstrates that variability reduction depends on the degree of correlation amongst participants' catches. In the best-case scenario, catch-pooling cooperatives can diversify away all season to season variation resulting from individuals' luck and skill, leaving only variation in fishery-wide harvest.

Selectivity, efficiency, and underwater observations of modified trap designs for the snow crab ( Chionoecetes opilio) fishery in Newfoundland and Labrador

Comparative fishing experiments were conducted to evaluate the selectivity and efficiency of escape mechanisms installed in traditional snow crab ( Chionoecetes opilio) traps. Performance of the different trap types (control, traditional, experimental) were compared on the basis of size distribution caught, numbers of animals per trap haul (CPUE N), and size selectivity. The study demonstrated that either 95 or 100 mm diameter escape mechanisms installed into traditional 14.0 cm mesh traps resulted in 38–47% fewer undersized pre-recruit (<95 mm CW) crab being captured, with no significant difference in the capture efficiency of standard (95–101 mm CW) or premium sized crab (>101 mm CW). Qualitative underwater behavioural observations were also conducted for snow crab in response to baited traps, corroborating current understandings as well as documenting new observations related to crab behaviour during capture, escape, haul-back, and interspecific competition with Atlantic cod ( Gadus morhua).

Development of performance indices for the Newfoundland and Labrador snow crab ( Chionoecetes opilio) fishery using data from a vessel monitoring system

This study investigates the potential for using data from a vessel monitoring system (VMS) to create indices of commercial fishery performance that may be used in monitoring snow crab resource status. Fishing hours were screened from hourly positional signals to create an index of fishing effort (hours fished) for comparison with that derived from logbooks (number of trap hauls). Similarly, a VMS-based fishing catch per unit of effort (CPUE) index was developed for comparison with CPUE derived from logbooks. Analysis of these indices showed that VMS-based fishing effort and CPUE indices can be interpreted to provide reliable complementary or alternative indices to logbooks for assessment of fishery performance in the Newfoundland and Labrador (NL) snow crab ( Chionoecetes opilio) fishery. We also developed a VMS-based index of fishing efficiency and illustrate how it can be applied toward understanding various behaviors and anomalies in the fishery. VMS data may offer other potential applications for snow crab assessment and management. Our approach and methods are applicable to other commercial fishery resources worldwide that are monitored using vessel monitoring systems.

Atlantic cod and snow crab predator–prey size relationship in the Gulf of St. Lawrence, Canada

Atlantic cod Gadus morhua stomach contents (n = 30 973, including 28 377 non-empty stomachs) and morphometric measurements on live snow crab Chionoecetes opilio and cod were examined to assess the predator-prey relationship between these 2 species. The most common snow crab instars found in cod stomachs were III and V (~6 to 8 and ~12 to 16 mm carapace width (CW), respectively) in the northern Gulf of St. Lawrence (GSL) and VI and VII (~17 to 23 and ~23 to 31 mm CW, respectively) in the southern GSL. A significant positive relationship was found between cod length and the largest and smallest CW of snow crab ingested by cod. Positive relationships were also found between gape width and body length in cod and between 3 measures of size (maximum span, width at rest, length at rest) and CW in snow crab. Snow crab length at rest was closely related to cod gape width, suggesting that the largest snow crab ingested by cod must be attacked from the side. There appears to be a plateau at 65.1 mm in the relationship between maximum snow crab CW and cod length, caused by the absence of large (adolescent and adult) male snow crab in cod stomachs. Other studies have found recently moulted, soft-shell snow crabs in cod stomachs, but this appears to be rare. Thus, snow crabs are susceptible to predation by cod mostly for the first 4 yr of post- settlement in the GSL. Any effect of cod predation on the snowcrab fishery would be felt 6 to 11 yr later, given growth models established for the GSL.

Fishing for social realities—Challenges to sustainable fisheries management in the Cape Horn Biosphere Reserve

Abstract Social-ecological complexity challenges conservation-oriented interventions even in settings with a small number of actors and conflicts involved. This article examines the development and trajectory of King and Snow Crab fisheries in the Cape Horn Biosphere Reserve (BR), the highly remote but globally connected Southern tip of the Americas. The feasibility of the Chilean legal instrument of Marine Management Areas (MMA) is assessed as a tool for mitigating impacts of overfishing in the area. Examining the local fishers’ perspectives in complement to a context analysis we find that external management models such as the MMA are not suited to make Cape Horn fisheries sustainable. Instead, efforts should be dedicated to a continuous process of stakeholder collaboration for developing site-specific management concepts and structures. These should be embedded in the larger BR initiative. Considering the area's particular conditions, several recommendations for such a process are formulated.

Patterns of fisheries institutional failure and success: Experience from the Southern Gulf of St. Lawrence snow crab fishery, in Nova Scotia, Canada

Abstract This paper examines why market and government institutions failed to prevent over fishing in the Southern Gulf snow crab fishery, whereas non-market institutions succeeded. A general conclusion is that the institutional environment in which economic behaviour must be coordinated for successful fisheries management is complex. More specifically, collective action dilemmas arise from the interdependency of human and fish species interactions. However, successful institutions are capable of resolving these dilemmas when they achieve credible commitment. Coordination mechanisms such as co-management contracts, horizontal patterns of communication and win–win negotiations all contribute to building an institutional arrangement in which participants are motivated to comply with conservation objectives.

Spatial evidence for information exchange and competition in the Gulf of St. Lawrence snow crab (Chionoecetes opilio) fishery

Throughout the 1990s, the Gulf of St. Lawrence snow crab (Chionoecetes opilio) harvest provided an example of effective co-management in a developing fishery. The Department of Fisheries and Oceans Canada (DFO) and the snow crab fleet (the fleet) shared information that coordinated management and exploitation throughout the season. A preseason survey by DFO provided resource distributions prior to the fishery's opening. In-season monitoring allowed managers to track spatial and temporal variation in crab availability. This level of detail allowed the application of the ideal free distribution as a management and conservation tool. However, proper justification for its application requires the demonstration of information exchange and competitive effects. The spatial distribution of effort suggests that both of these are present. Fishing effort was influenced by public information and potential information exchange within the fleet. Reduced aggregation at smaller spatial scales suggests competition in trap placement. Thus, increasing fleet size may have a disproportionately small impact on fishing mortality because of limitations in information exchange and the lack of personal information in the new vessels. However, the nonlinear relationship between crab abundance and catch rates suggests that managers should avoid policies that increase fishing effort during times of low crab abundance.

A Rapid, High‐Throughput Technique for Detecting Tanner Crabs Chionoecetes bairdi Illegally Taken in Alaska's Snow Crab Fishery

AbstractTanner crabs Chionoecetes bairdi and snow crabs C. opilio are both important commercial species for Alaskan fisheries. The geographical ranges of Tanner and snow crabs overlap in the southeastern Bering Sea where a commercial fishery targets the more abundant snow crabs. Morphological identification of these species and of hybrids has proven difficult and impedes monitoring of the harvests. Techniques for the genetic identification of these species have been developed, but it may not be possible to process the desired number of samples because of throughput limitations and sample requirement constraints. Here we present a rapid, high‐throughput assay for identifying these species based on single nucleotide polymorphisms (SNPs) in the nuclear rRNA internal transcribed spacer 1 region and the mitochondrial DNA 16S rRNA gene. These SNPs can also be used to infer the direction of hybridization (i.e., the species of each gender).

Estimating Handling Mortality Due to Air Exposure: Development and Application of Thermal Models for the Bering Sea Snow Crab Fishery

AbstractThe fishery for snow crabs Chionoecetes opilio in Alaska occurs during the winter, and handling mortality may be high due to cold‐air exposure. Heat budget models that include convection, evaporation, long‐wave radiation, and solar radiation were developed for snow crabs. Model performance was evaluated by comparing observed and predicted temperatures of live crabs exposed to cold air. The model performed well, predicting temperatures of the body, legs, and eyes within 1.5°C. Legs and eyes cooled faster than the body and may be more susceptible to cold‐air exposure. Weather variables were ranked in the following order of importance: (1) air temperature, (2) solar radiation, (3) wind speed, (4) humidity, and (5) cloud cover. Clear, cold, breezy nights are the most detrimental conditions for crabs. Hourly weather records from a site near the fishing grounds were used in conjunction with the thermal model to estimate cooling rates for crabs every hour during actual and hypothetical seasons. The probability of damage for various cooling rates was estimated based on previously published laboratory data. Discard handling damage rates were highly variable, ranging from 0% to 30% over 21 actual fishing seasons. Damage rates for hypothetical seasons that varied in length, start day, and daily fishing hours were calculated. Damage rates were reduced by delaying the start day (15 January) until 1 March as well as by limiting fishing time to daylight hours. Combining a later starting day with limited fishing hours resulted in 90% of the hypothetical seasons having damage rates of 10% or less. Generally, longer seasons had lower damage rates, especially when fishing hours were limited. Although developed for cold‐weather Alaska fisheries, this approach can easily be adapted to other fisheries where handling mortality due to temperature changes during capture is a concern.

Epidemiology of bitter crab disease (Hematodinium sp.) in snow crabs Chionoecetes opilio from Newfoundland, Canada

The parasitic dinoflagellate Hematodinium sp. causes a condition known as bitter crab disease (BCD) in snow crabs Chionoecetes opilio and Tanner crabs C. bairdi. As the name of the condition implies, crabs infected with BCD are unmarketable due to their bitter flavor. We surveyed the distribution of BCD in 3 regions within the snow crab fishery of Newfoundland from 1997 to 2003. Over time, the disease has become firmly established in Conception and Bonavista Bays and persists at low levels on the Avalon fishing grounds. An epizootic occurred within Bonavista and Conception Bays in 1999 and persisted in Conception Bay in 2000, reaching prevalences of over 2% to 9% in trapped and trawled male crabs and from 19 to 26% in trawled and trapped female crabs, respectively. Infections were highest in females and small males, i.e. the unfished and pre-recruit portions of the fishery. In a mortality study, all of the naturally infected crabs died and 50% of the experimentally inoculated crabs died. Patterns in the molting cycle and prevalence of infection indicate that transmission occurs during the post-molt condition, and that overt infections probably develop 2 to 4 mo later with mortalities occurring at least 3 to 4 mo thereafter. The hydrography of this bay may have contributed to the epizootic as infections were centered within the deeper confines of the bay. Analysis of various abiotic factors uncovered a significant positive association between prevalence, depth and mud/sand substrates; the nature of this relationship was not apparent but may be related to diet or alternate hosts. Lastly, given the increase in BCD in snow crabs in Newfoundland, we recommend that fishery management programs for Chionoecetes fisheries employ non-selective gear to monitor for Hematodinium infections in female and juvenile crabs because these under-sampled members of the population may forewarn of impending recruitment declines that might otherwise remain unexplained.

Comment — An improved link between industry, management and science: review of case history of the southwestern Gulf of St. Lawrence snow crab fisher

A recent review by Loch et al. (1995) portrayed the snow crab (Chionoecetes opilio) exploitation in the southwestern Gulf of Saint Lawrence (eastern Canada) as an exemplary fishery. Industry involvement, better management practices, a unique method for evaluating exploitable biomass, and major insights into the biology of C. opilio were said to have contributed to rebuilding this snow crab stock after a 1987–1989 fishery collapse. I am compelled to reply to Loch and co-authors for two reasons. First, their review contains several unsubstantiated claims and is based on incomplete citation of literature. My commentary addresses only those scientific issues that are critical to resource management and conservation, drawing on information and literature available to the authors in 1994. Second, their review leaves the impression that directed human intervention was a major factor in the increase of the snow crab stock of the southwestern Gulf. While applauding recent advances in science and management, I point out that other snow crab fisheries in eastern Canada also declined between 1985 and 1989 and since then have fared just as well as the snow crab fishery in the southwestern Gulf. This may to a large extent reflect the effects of natural population fluctuations and of environmental change on the levels of fishery recruitment, rather than the effects of regional exploitation and management initiatives.

Reply — An improved link between industry, management and science: review of case history of the southwestern Gulf of St. Lawrence snow crab fisher

Loch et al. (1995) examined the recovery of the southwestern Gulf of St. Lawrence snow crab fishery after its nearly collapsed situation in 1988–1989 by highlighting industry involvement, better management practices, and a new survey method. This review did not elucidate underlying biological events but rather emphasized the relationship established among science, management, and industry, which resulted in a unique partnership between the Department of Fisheries and Oceans and industry. Nevertheless, some readers have the impression that the recovery of the snow crab stock was because of the good fishery management and not underlying biological events (Sainte-Marie 1997). In addition, there are some unclear statements that may mislead the reader about the general consensus of Canadian snow crab biologists on snow crab stock dynamics and management approach. Therefore, this response deals with further clarification of Loch et al. (1995) by including the most up to date accounts of developments in snow crab biology and stock assessment in eastern Canada.

Reply - An improved link between industry, management and science: review of case history of the southwestern Gulf of St. Lawrence snow crab fishery

Reply - An improved link between industry, management and science: review of case history of the southwestern Gulf of St. Lawrence snow crab fishery

Comment - An improved link between industry, management and science: review of case history of the southwestern Gulf of St. Lawrence snow crab fishery

Comment - An improved link between industry, management and science: review of case history of the southwestern Gulf of St. Lawrence snow crab fishery