Fig 1 - uploaded by Shijie Zhou
Content may be subject to copyright.
Dimensions (cm) of simulated standard king crab pot (pot A). The newly designed pot (pot B) is the same size and shape as pot A but has two lower and wider entrances, one-way opening triggers, and smaller mesh.
Source publication
We conducted a laboratory experiment to compare effectiveness of two pot designs in reducing the bycatch of female and sublegal-sized male red king crabs (Paralithodes camtschaticus) while retaining legal males. One pot (pot A) was a simulated standard king crab pot; a newly designed pot (pot B) had smaller mesh size, lower and wider entrances, and...
Contexts in source publication
Context 1
... various pots (unpublished data; High and Worlund 1979). A pot with dimensions of 100 × 100 × 60 cm was used as a simulated standard king crab pot in this study. The two entrance open- ings were 90 × 20 cm. Tar-treated knotted nylon mesh of 15.2 cm stretch mesh was used for the web. This simulated standard pot is referred to as pot A in this paper (Fig. ...
Context 2
... new pot (pot B) which we designed had the same dimension and shape as pot A, but the tunnels, entrances, and mesh size differed. The two entrances were lowered from 40 cm in pot A to 20 cm, and widened from 90 cm in pot A to the entire length of one side of the pot (100 cm; Fig. 1). Vertical bars (made from PVC pipe) with the upper end attaching to a horizon reebar and the down end free (called triggers) were rigged on each entrance to allow inward opening ...
Similar publications
1. During the 2009/10 season, 17.7 tonnes of giant crab were harvested from South Australian waters. Most of this catch (71%) was harvested by two miscellaneous licence holders. Rock lobster fishers with giant crab quota entitlements accounted for 23% of the total, while the remainder (6%) was taken as by-product by commercial rock lobster fisherme...
1. During the 2008/09 season, 21 tonnes of giant crab were harvested from South Australian waters. Most of this catch (74%) was harvested by two miscellaneous licence holders. Rock lobster fishers with giant crab quota entitlements accounted for 17% of the total, while the remainder (9%) was taken as by-product by commercial rock lobster fishermen...
1. During the 2010/11 season, 18.8 tonnes of Giant Crab were harvested from South Australian waters. Most of this catch (73%) was harvested by Miscellaneous licence holders. Rock Lobster fishers with giant crab quota entitlements accounted for 25% of the total, while the remainder (2%) was taken as by-product by commercial Rock Lobster fishermen no...
Looking for alternative resources to the Juan Fernandez spiny rock lobster ( Jasus frontalis), the traditional target species of the artisanal fishermen of the archipelago, an exploratory fishing campaign with fishing pots was conducted around Robinson Crusoe and Santa Clara islands. Between November 11, 1996, and March 23, 1997, a total of 71 fish...
High-level classifications of Anomura typically recognize three major clades: Galatheoidea (squat lobsters and porcelain crabs), Paguroidea (hermit and king crabs), and Hippoidea (mole crabs). The general stability of this classification, however, has masked the vigorous debate over internal rela-tionships. Phylogenetic relationships of the Anomura...
Citations
... As increases were observed for legal sized crab that were not evident in concurrently fished pots with larger mesh, the implication is that smaller mesh enhanced entrance rates of crab. A similar finding has been demonstrated for red king crab (Paralithodes camtschaticus) in laboratory trials (Zhou and Shirley, 1997). The potential of small meshes to increase capture efficiency in the Barents Sea fishery therefore exists. ...
... We hypothesize that the smaller meshes made exploratory behaviour on the pot walls easier, by presenting a larger surface area for climbing crab. For red king crab, small meshed pots encouraged exploratory behaviour as individuals were unable to reach through and were therefore forced to attempt to gain access to the bait in other ways (Zhou and Shirley, 1997). This ultimately resulted in higher entrance rates. ...
In the Barents Sea Norwegian pot fishery for snow crab (Chionoecetes opilio), fishing effort regulations and bait expenses create incentives to improve the catch rates. The fishery also currently captures a large proportion of sub-legal sized crab which must be sorted out and released. In this study, we used comparative fishing trials to determine the size dependent capture efficiency of three modified pot types designed to address these issues. A pot constructed with 40 mm mesh caught ∼35% more (CPUE, number of individuals per soak time) large crab (≥ 100 mm carapace width [CW]) than the pot typically used in the commercial fishery (140 mm mesh). However, it also retained massive amounts of small individuals (< 100 mm CW). The addition of four stadium shaped escape openings into the 40 mm and 140 mm mesh designs resulted in large reductions in catches of small crab, but also a ∼30% reduction in large crab. Analysis of size dependent catch comparison rates and selectivity parameters supported the CPUE findings. Of the tested designs, catches were best optimized by the currently used commercial pot. However, we conclude that a small mesh pot with escape openings has the potential to increase catches of large crab and reduce catches of non-commercial small crab. Further development of this design, particularly in terms of the dimensions of the escape openings, is therefore required.
... Broadhurst et al. 2019). Furthermore, these variables can interact; crabs have been shown to be more motivated to find the entrance funnels of traps with a smaller mesh size, because crabs are less able to access the bait by inserting their chelipeds through the mesh (Zhou and Shirley 1997); hence, a greater number of funnels may improve efficacy. Thus, choosing appropriate design features that are most effective for the particular objectives under investigation is important when using traps in independent surveys. ...
Surveying free-ranging crab populations is important for monitoring the health of exploited stocks and predicting future productivity. Here, we present a novel research trap design for use in fisheries-independent surveys of blue swimmer crab (Portunus armatus) populations, and evaluate the trap against some existing approaches within an independent survey framework. Specifically, the trap design aimed to improve efficiency for capturing smaller crabs, without adversely affecting catches of larger crabs. We quantify and report the abundance and selectivity of these traps, relative to co-located samples obtained using beam trawls and standard commercial round traps, to establish whether these small-mesh traps may offer any improvements over existing survey methods. Comparison and evaluation of these small-mesh traps against other existing survey gear, in different places and at different times, showed that the traps are more effective at catching smaller crabs when they are present, and equally or more effective at catching larger size classes of crabs. The beam trawl appeared to be effective at capturing a reasonable size range of crabs; however, the number of crabs caught (using a similar investment of time) was substantially lower than that caught in traps. This novel small-mesh research trap appears suitable for fisheries-independent surveys of portunid crab species.
... Significant improvements, resulting in successive decreases in the coefficient of variation (CV) of CPUE data, have been achieved over the 30-year survey time series. These include a move from fixed to random pot locations and stratification of survey areas in 1986; a gradual shift from square to cone pots over the period 1995-1999 (Zhou and Shirley 1997); restratification of the survey to redefine strata boundaries based upon the CPUE of legal, sublegal, and female red king crab in 2005 (Clark 2008); and, most recently, an increase in the number of pots set in each surveyed area to improve the precision of survey area estimates. A detailed timeline and methods of survey development is outlined in Clark (2008) and Clark et al. (2003). ...
This report reviews the commercial and personal use fisheries for red and blue king crab in Region I, which includes Registration Area A (Southeast Alaska) and Registration Area D (Yakutat). The commercial red and blue king crab harvest in Southeast Alaska totaled 120,566 lb valued at $1.2 million during the 2017/18 season, which was the last season the fishery was open. The average dock price per pound for red and blue king crab during that season was $9.95. The red king crab fishery in Southeast Alaska is fully developed. Red king crab stocks in Southeast Alaska are assessed in an annual Alaska Department of Fish and Game red king crab pot survey that began in 1979. There have no stock
assessment surveys for Yakutat red king crab stocks and harvests in this area have been sporadic and relatively low. The Southeast Alaska commercial red king crab fishery and the personal use red king crab fishery in Section 11-A are managed based on biomass identified in the annual survey. The personal use red king crab fishery outside of Section
11-A is managed by bag and possession limits and area-specific closures defined through emergency orders. Dockside sampling and skipper interviews also are routinely conducted in Southeast Alaska commercial red and blue king crab fisheries.
... The crab must walk along the pot wall to find the entrance. The average time to search for the entrance was 1.7 min and 2.9 min (Zhou and Shirley, 1997). The swimming crabs failed to enter the pot because the crab did not find the entrance (Martasuganda, 2008). ...
The behavior of blue swimming crab (BSC) (Portunus pelagicus) to the collapsible pot is observed to redesign the entrance of the pot with high effectiveness. The purpose of this study is to analyze the behavior response of BSC to the entrance gate of the collapsible pot by laboratory experiments. The behavior response of the BSC (100-150 mm of carapace width (CW), n= 15) to the two angles of the entrance gate, that were 200 as control and 400 as a modification of the collapsible pot. The movement and speed of the crab to the entrance gate were observed by using CCTV Camera. The results showed that the percentage of crabs failed to find the entrance was higher than crab that be successful to enter the pot. The crab that failed to find the entrance was 43% for control and 52% for modification pot, while the crab that be successful to enter was 24% for control pot and 19% for modification pot. There were five movement patterns of crab to the pot i.e. straight to entrance, side to entrance, side to side, entrance to side, and straight to side. The average speed of entrance crab was 127.89 ± 46.48 for control, and 88.45 ± 5.74 for modification pot. Keywords: behavior, response, blue swimming crab, collapsible pot, Portunus pelagicus
... Traps are passive and stationary fishing gears that can be deployed individually or in strings with a variety of shapes and sizes, and are widely used for harvesting a variety of crab species such as snow crab Chionoecetes opilio (Nguyen et al., 2017, red king crab Paralithodes camtschaticus (Zhou and Shirley, 1997), green crab Carcinus maenas (Bergshoeff et al., 2019), giant mud crab Scylla serrata (Broadhurst et al., 2020), and swimming crab Portunus pelagicus (Boutson et al., 2008) throughout the world. Given the importance of this fishing technology, a substantial number of studies have been investigated during the past few decades to reduce bycatch (Major et al., 2017), and to improve size selectivity (Hébert et al., 2001;Walsh, 2007, 2011;Olsen et al., 2019a;Broadhurst et al., 2020), bait usage (Araya-Schmidt et al., 2019Favaro et al., 2020), trap design (Bergshoeff et al., 2019;Olsen et al., 2019b), and catch rate (Butcher et al., 2012). ...
The swimming crab Charybdis feriata fishery is important to the coastal fishing communities of Vietnam, particularly in the province of Quang Nam. Trapping is considered a low impact and fuel-efficient fisheries capture technique that is drawing increasing attention as concerns regarding the impact of fisheries on ecosystems and the environment grow. However, traps typically have low capture efficiency for most crab species and there is considerable interest to improve catchability. In this study we investigated the impact of modifying the number of trap entrances on a traditional trap design, and also the colour of entrance-netting, on the catch rate of swimming crab in the Vietnam trap fishery. In the first experiment we compared catch rates between a traditional three-entrance trap and a modified one-entrance trap design, and found that the modified one-entrance trap had a 24 % higher catch rate. In second experiment, we compared catch rates of one-entrance traps having green or yellow entrance-netting and found that yellow netting increased catch rates by 31 %. This study shows that fishing enterprises could improve their swimming crab trap fishery by using modified one-entrance traps with yellow entrance netting.
... The square top and bottom of commercial cod pots range between 150 to 240cm in length and width. The walls of the pot range between 67 to 99 cm high (Zhou and Shirley 1997). Pots were set between 82 and 119 meters deep and allowed to soak for 6 to 12 hours before being hauled. ...
... Sloping entrances upwards, installing separate chambers and fitting shutters or triggers that close the entrance opening after the target animal have commonly been used (Thomas 1959;High 1976;Miller 1978Miller , 1980Miller , 1990. Other methods include slippery plastic collars installed in top-entry pots (Miller 1980) and one-way triggers fitted on open entrances (High 1976;Zhou and Shirley 1997). ...
Fishing trials targeting several invasive swimming crab species in their native habitat were undertaken using two types of collapsible pot, one with open-eyed entrances and the other with closed-eyed entrances, to analyse differences in catch retention between them. The open-eyed pot was dome-shaped with two funnel entrances located at opposite ends, whereas the closed-eyed pot had two soft sleeves that ended in slits and had to be pushed through by organisms to ingress, supposedly reducing escape. Retention fishing trials (100 pot hauls per pot type) using a 1-day soaking and fish bait confirmed no significant difference in crab catches between pot types; differences were only detected for large fish (morays and congers). A second set of 4-day escape trials (20 pots per type) was undertaken to investigate how long organisms would be detained in the pots. Escape was significantly affected, and half-residences were typically delayed by 1-2 days for most crabs and fish in closed-eyed entrance pots because the entrances closed. Closed-eyed entrances hampered escape and may be useful when longer soakings are needed; however, because no differences were detected in crab numbers between the two entrance types for short soakings, we recommend open-eyed entrance pots in order to mitigate possible ghost fishing effects from lost gear.
... Standard traps have mesh sizes ranging from 9 to 20 cm. Zhou and Shirley (1997d) designed and tested an experimental trap with smaller mesh (47 mm), lower entrance opening (20 vs. 40 cm), wider entrance (100 vs. 90 cm), and vertical triggers spaced 13 cm apart (vs. none). ...
... King crabs that approach standard traps insert their chelipeds through the mesh and stay in one location for a period of time trying to enter the trap (Zhou and Shirley, 1997a). King crabs that approached the experimental trap were not able to insert their chelae through the mesh and moved more often, thus improving their chances of finding the entrance (Zhou and Shirley, 1997d). Time spent searching for the entrance decreased from a mean of 2.9 ± 9.2 min for the standard trap (range 1-109 m) to 1.2 ± 2.9 min (range 1-20 min) for the experimental trap (Zhou and Shirley, 1997d). ...
... King crabs that approached the experimental trap were not able to insert their chelae through the mesh and moved more often, thus improving their chances of finding the entrance (Zhou and Shirley, 1997d). Time spent searching for the entrance decreased from a mean of 2.9 ± 9.2 min for the standard trap (range 1-109 m) to 1.2 ± 2.9 min (range 1-20 min) for the experimental trap (Zhou and Shirley, 1997d). The probability that a legal male RKC would enter the trap after encountering it increased from 0.159 for the standard trap to 0.612 for the experimental trap, an increase of 285%. ...
... Further, while traps fitted with 85mm × 55-mm escape gaps reduced catches of undersized crabs without affecting catches of legal-size crabs in most cases, our size-selectivity analyses indicated that the probability of retaining undersized crabs was larger in this treatment (about 40%) than in traps with 95-mm × 55-mm escape gaps (about 16%). By comparison, the size-selectivity analyses showed that the 45-mm-high treatments (i.e., 85 × 45 mm and 95 × 45 mm) both retained relatively large proportions of undersized crabs (>50%), indicating that the escapement of crabs was being limited by their height, rather than width, which is consistent with studies of other species of crab elsewhere (Brown 1982;Zhou and Shirley 1997). ...
In response to experimental evidence and anecdotal concern about bycatch in the net‐covered traps used increasingly by recreational and commercial fishers to target giant mud crabs Scylla serrata in New South Wales, Australia, experiments were done to examine the utility of escape gaps in reducing the bycatch of Yellowfin Bream Acanthopagrus australis (also known as Surf Bream) and undersized giant mud crabs. In each of two rivers, 10 different treatments comprising four different sizes of rectangular, horizontal escape gaps (85 × 45 mm, 85 × 55 mm, 95 × 45 mm, and 95 × 55 mm) and a control (no escape gaps) applied to both two‐entrance and four‐entrance traps were tested separately during the day and night. Traps fitted with escape gaps reduced the mean numbers of Yellowfin Bream and undersized giant mud crabs by 53–78% and 58–84%, respectively. Despite some inconsistent results, the effect of escape gaps was statistically significant in four of the seven analyses. There were, however, no significant differences in the mean numbers of Yellowfin Bream and undersized giant mud crabs among the different sizes of escape gap. By contrast, the largest escape gap treatment (i.e., 95 × 55 mm) reduced the mean number of legal‐size giant mud crabs by 35–41%, which was significant in one of four analyses. Moreover, size‐selectivity analyses indicated that the largest escape gap also allowed a comparatively greater proportion of undersized mud crabs to escape. Our findings show that implementing an 85‐mm × 55‐mm escape gap could substantially reduce bycatch without affecting catches of the target organism. Further reductions in catches of undersized giant mud crabs is possible with the 95‐mm × 55‐mm treatment, but at the cost of some reduction in the catch target.
Received August 19, 2011; accepted December 11, 2012
... During the attraction phase, red king crabs encounter olfactory stimuli and at closer range they also perceive visual stimuli (Miller 1979;Zhou and Shirley 1997a). Moreover, red king crabs already feeding in the pot may produce sounds to which other red king crabs can respond (Tolstoganova 2002), and once they are in physical contact with the pots, red king crabs are exposed to tactile stimuli from the net (Zhou and Shirley 1997b). Thus, red king crabs are successively or simultaneously exposed to a multitude of stimuli that may interact and either compete or reinforce each other. ...
... A red king crab's activities related to a pot were categorized into five categories: approach, entrance search, leaving, entry, and exit (see Zhou and Shirley 1997b for detailed definitions). The entrance search was further divided into a horizontal phase and a vertical phase. ...
Interactions between the food search behavior of the red king crab Paralithodes camtschaticus and pot design and the consequences for entry success were studied in situ with a square pot with two funnels on opposite sides and a conical pot with one vertical funnel at the top. Red king crabs that approached the pots upcurrent were chemically stimulated and appeared to be locked onto the odor plume, whereas those that approached the pots across-current showed more flexible search behavior. The location of the funnels meant that entry also requireed a vertical search phase. Forty percent of the red king crabs encountering the pots performed vertical searches on each type of pot, but the probability of entry once a vertical search had commenced was 20 times as high for the square pot as for the conical pot. Chemically stimulated red king crabs limited their vertical search to the bait plume. The location of the bait relative to the entrance may have caused chemically stimulated rheotaxis to lead red king crabs all the way into the square pots, in contrast to the conical pots for which the entrance is higher than the extension of the plume. These results demonstrate the importance of including both horizontal and vertical dimensions in behavioral studies of the catch efficiency of crab pots.
