Catching Performance Research Articles

Structure and composition of the macrobenthic community associated to shallow mangrove-seagrass habitat along the southern Red Sea coast, Saudi Arabia

Macrobenthic communities in shallow mangrove-seagrass habitat at the southern portion of Saudi Arabia, Red Sea were explored to (i) characterize their diversity and abundance; (ii) examine the variability among outer, middle and inner stations; and (iii) evaluate the catch performance of scoop (bulldozer) and Van Veen grab. Fifteen sampling collections (9 scoop and 6 grab) captured 4,491 individuals encompassing 18 taxonomic groups. Polychaetes predominated the samples, followed by pelecypods, gammarids, gastropods, and isopods. The species richness did not differ among stations. The density of macrobenthos was significantly (ANOVA, F = 5.51, p = 0.020) higher in the outer and middle stations than the inner station. Moreover, the difference of macrobenthos abundance was seemingly associated with the sediment type and the presence and absence of seagrass. The proportion of non-shared groups over the total number of groups increases from the outer to the inner stations (30.7 to 57.1%), which revealed a degree of difference in the community. The exclusive presence of stomatopods in the inner station suggests their territorial behavior. As well, Van Veen grab captured higher taxonomic groups than scoop; the difference in abundance was not significant. Grab was more pragmatic with ease to operate and thus higher catch efficiency.

Paraketa balıkçılığında kullanılan farklı yemlerin avcılık performansı ve olta iğnesinde kalma oranı

In this study, the catch performance and remaining ratio on fishing hooks of natural alive mud shrimp (Upogebia pusilla) (CCK), siliconized mud shrimp (SCK) and siliconized pellet (SP) were investigated in a longline. The trials were carried out monthly between May 2016 and April 2017 in Zeytinlikuyu district of Kıyıkislacik Village – Milas-Mugla province. The main body diameter has 0.70 mm, leader and snoods have 0.40 mm. The snood length and distance is 1.5 m and 4.0 m, respectively. 14 no straight hooks were used. Totally 150 hooks, 50 for each bait were used and each bait was replaced in 25 hooks. The individuals caught during the samplings were separated as CCK, SCK and SP, and each individual was measured as the precision of mm the total length (TL) and weighted of 0.01 g. Totally 191 individuals from seven families with 18 different species were caught. Gilthead sea bream (Sparus aurata) was the abundant species with 48.7% in all bait type, and the followed by common pandora (Pagellus erythrinus) with 10.5%, common two-banded sea bream (Diplodus vulgaris) with 9.4% and annular sea bream (Diplodus annularis) with 8.9%. Of the 191 individuals, 55% (105 individuals) were caught with CCK, 33.5% (64 individuals) with SCK and 11.5% (22 individuals) with SP. The results of the trial with 3 different bait types were shoved that that there are significant differences between the catch rates of gilthead sea bream, annular and common two-banded sea bream (χ2, P<0.05). In paired tests between bait groups (CCK-SCK, CCK-SP and SCK-SP), there were no clear differences between the sizes of the individuals (ANOVA, P>0.05). Catch per unit effort (CPUE) values of CCK, SCK and SP were calculated as 0.05 n/h, 0.03 n/h and 0.01 n/h, respectively. In the same order, yield per unit effort (YPUE) values were determined as 7.28 g/h, 4.35 g/h and 2.99 g/h. When the remaining rate of baits on the hooks were evaluated, CCK gave the lowest rate with 6.32%2.01. It is thought that SCK should be used as an alternative particularly when natural mud shrimp cannot be utilized as alive or unable to be supplied due to the cold weather conditions and time restrictions. On the other hand, it is thought that performing such studies with bait made with natural binders such as gelatine instead of silicone will be extremely important in terms of less harm to both fish and nature.

Use of the traditional halibut hook of the Makah Tribe, the čibu.d, reduces bycatch in recreational halibut fisheries.

A previous study found that use of the traditional halibut hook (čibu.d) of the Makah Tribe in present day recreational Pacific halibut (Hippoglossus stenolepis) fisheries significantly reduced bycatch compared to paired 8/0 circle hooks. The study also found that the čibu.d had a significantly reduced catch of halibut, but that the reduction may have been due to manufacturing flaws in the čibu.d used in the study. In this two-phased study, we first compared the fishing performance of redesigned čibu.d made from four different materials: brass, stainless steel, plastic, and wood. In the second phase, we compared the fishing performance of the brass čibu.d with two common recreational fishing set-ups: a single large 16/0 circle hook and paired 8/0 circle hooks. The fishing performance of the redesigned čibu.d was not statistically different for čibu.d made of brass, stainless steel, or plastic. However, the čibu.d made from wood had significantly lower catch of halibut than the other čibu.d. We selected the brass čibu.d for the second phase of the study for continuity with the previous study of čibu.d and found that it had significantly less bycatch and a lower bycatch ratio than both the paired 8/0 and single 16/0 circle hooks. No significant differences were found in catch rates of halibut for paired 8/0 circle hooks, 16/0 circle hook, and the brass čibu.d. This study demonstrates that the improved catching performance of čibu.d on halibut and reduced bycatch compared to other popular approaches can be achieved by using brass čibu.d. Managers of recreational halibut fisheries should consider the use of čibu.d in areas where bycatch is a concern.

Effect of a lateral square-mesh panel on the catch pattern and catch efficiency in a Mediterranean bottom trawl fishery

The current legal codends used in Mediterranean bottom trawl fisheries are at high risk of retaining undersized individuals of several commercial fish species. This entails that codends alone are unable to provide the desired exploitation pattern. A simple technological measure that potentially can provide higher release efficiency of undersized fish are Square-Mesh Panels (SMPs). SMPs are often applied in the upper section of the trawl belly, just ahead the codend. However, recent studies in the Mediterranean have demonstrated that SMPs mounted in this position provided limited release efficiency, because very few fish came into contact with their meshes. In attempt to improve SMPs efficiency in the Mediterranean bottom trawl fisheries, we applied them on the lateral sides of the last tapered section of the trawl belly, just ahead of the codend, and fitted two guiding panels in the trawl belly to enhance fish-SMP contact. We compared the catch performance of a standard commercial trawl with a 52 mm diamond-mesh codend and of a similar trawl fitted with lateral SMPs (70 mm mesh size) in the belly using a twin trawl. The study focused on red mullet (Mullus barbatus), a commercially important species, but data for gurnard (Chelidonichthys lucerna and Chelidonichthys cuculus) were also obtained and analysed. In contrast to previous research on SMPs mounted in the top panel of the trawl, in this study SMPs induced a significant effect on catch performance for red mullet, demonstrating that their lateral position involved greater fish-SMP contact. However, since the test trawl lost a significant amount of legal-sized red mullet compared with the standard trawl, the effect was not wholly positive, possibly due to an excessively large mesh size. Therefore, future studies should be encouraged to test lateral SMPs with smaller mesh sizes.

Comparative analysis of the diet composition and its relation to morphological characteristics in Achirus mazatlanus and Syacium ovale (Pleuronectiformes: Osteichthyes) from a Mexican Pacific coastal lagoon

ABSTRACT The purpose of this research was to investigate differences in diet composition between Achirus mazatlanus and Syacium ovale, two flatfishes inhabiting in a tropical coastal lagoon and to investigate the relationship of their feeding habits to size, body morphometry and mouths characteristics. Fish were collected during sampling trips conducted regularly from 2011 to 2016 using several types of fishing gear. Total number of analyzed stomachs with some food content was 328 for Achirus mazatlanus from 1.4 to 21.3 cm total length (TL) and 203 for Syacium ovale with 1.3 to 24.0 cm TL. Results indicate that both species share a general diet based on benthic invertebrates and fishes but S. ovale has a more piscivorous habit, which can be explained by a more slender body shape and larger teeth, characteristics which increase prey fish catching performance. Important changes in composition of food categories related to size were not found for any species, but larger fish of both species eat larger ranges of prey sizes, and this ontogenetic change is consistent with recent developments on optimal foraging theory.

Comparative study on the full-scale prediction performance of four trawl nets used in the coastal bottom trawl fishery by flume tank experimental investigation

Energy efficiency, catchability, and ecological sustainability have become important issues for coastal bottom trawl fisheries. Thus, fishing gear has been modified to increase the swept area and decrease the drag and bycatch. To evaluate the effect of twine thickness, twine material, and mesh size on the drag (bridle tension) and geometrical shape of trawl nets, this study focused on the full-scale prediction performance (geometry and resistance) of bottom trawl nets used in the coastal fishery. Four 1/18-scale bottom trawl models with different twine diameters, different mesh sizes, and even the Geometrical shape of wing-end were designed and tested in a flume tank at Tokyo University of Marine Sciences and Technology (TUMST). The flume tank experimental data were evaluated to predict full-scale performance at sea and to compare the performance of trawl nets built with traditional materials (polyethylene), namely, trawl nets 1 and 4, with those built with innovative materials (Dyneema and nylon monofilament), namely, trawl nets 2 and 3, respectively. The geometrical shape of bottom trawl net was determined from the nonlinear equation constructed and solved using the experimental data with various door spreads and towing speeds. The results show that an increase in mesh size using Dyneema (trawl net 2) systematically leads to a decrease in bridle tension ~ 34.55%, a decrease of twine diameter using nylon monofilament (trawl net 3) lead to a decrease in bridle tension ~ 35.4%, and an increase in mesh size using triangular shape in the wing-end (trawl net 4) lead to a decrease in bridle tension ~ 19.92%. The net mouth area of trawl net 1 is 4.36%, 10.88%, and 6.47% greater than those of trawl nets 2, 3, and 4, respectively. The filtered volume of trawl net 3 is 1.29%, 7.48%, and 4.13% greater than those of trawl nets 1, 2, and 4, respectively, indicating that trawl net 3 has better catch performance than other trawl nets. The shapes of floating rope of all the four trawl nets are very close with a gap of less than 1.5%, indicating that the increase in mesh size and decrease in twine diameter do not affect the geometrical shape significantly as the drag force. The results also show that the ratio between bridle tension and net mouth area of trawl net 1 is 31.57 %, 27.61%, and 14.37% greater than those of trawl nets 2, 3, and 4, respectively.

A trap with light-emitting diode (LED) lights: Evaluating the effect of location and orientation of lights on the catch rate of snow crab (Chionoecetes opilio)

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.

Influence of Crab Trap Geometry and Wind Direction over the Catch Fluctuations in a Neotropical Coastal Lagoon

Blue crabs (Callinectes spp.) are widely distributed around coastal regions being usually exploited by artisanal fishing through specific fishing gears, like as crab traps. Notably, two crab traps types are adopted in Brazil: (I) rectangular crab traps and (II) circular crab traps. Empirically, fishermen suggest that the geometry of these fishing gears amongst the wind regimes in shallow waters are directly related to the catch success, that is, the blue crabs capture into the crab traps. However, these empirical observations have not been proven by academy. Thus, the present study analysed the performance of circular and rectangular traps during twenty campaigns in a coastal lagoon located in Laguna, Santa Catarina–Brazil. The results showed that circular crab traps obtained the highest catches of Callinectes spp. than rectangular crab traps. We observed that wind direction can influence the catch performance in both fishing gears and the best catch performance in our study region were during NE and SO wind quadrants.

Assessment of the relative catch performance of hake, red mullet and striped red mullet in a modified trawl extension with T90 netting

We studied the relative catch performance of a modified trawl fitted with an extension piece using a 90º turned mesh (T90) in comparison with a standard trawl net used in NW Mediterranean bottom trawl fisheries employing a diamond mesh net. The comparison was made by means of paired experimental hauls using the same fishing vessel with alternate deployments of the standard net (control) and the experimental net. We used the catch comparison approach for three target species of the fishery: European hake, red mullet and striped red mullet. Our results show that the experimental net significantly reduces the catches of small-size hake and red mullet (though there was no discernible difference for striped red mullet), reducing unwanted catches of regulated species under the Landings Obligation. The overall catch rates of hake, pooled over all sizes, also increased by an estimated 50%, while the catch rates of red mullet and striped red mullet were significantly lower. However, considering all commercial species, the experimental net produced losses of commercial catch and income estimated at 17% and 18%, respectively, which may pose a barrier to the adoption of this relatively simple, inexpensive solution.

Visual tracking behaviour of two-handed catching in boys with developmental coordination disorder

BackgroundDevelopmental coordination disorder (DCD) is a motor learning disability that affects coordination resulting in an inability to perform movement skills at an age appropriate level. One area suspected to contribute to the movement difficulties experienced are deficits in visuomotor control. AimsThis study investigated visual tracking behaviour during catching in children with DCD. Methods and proceduresTwenty-four boys completed the study: 11 with DCD (9.43 years ±0.73) and 13 controls (9.16 years ± 0.68). Participants performed 10 central catching trials, with the best five used to evaluate tracking behaviour and motor responses. Outcomes and resultsPrior to ball release, the DCD group exhibited more fixations (p = 0.043) of lesser duration (p = 0.045). During flight, the DCD group took longer to initiate smooth pursuit (p = 0.003) however, once initiated, both groups were effectively able to maintain smooth pursuit. Despite initial delays, these had no impact on movement initiation time (p = 0.173), however, movement time was significantly slower in the DCD group (p = 0.031). Conclusions and implicationsThe results of this study demonstrate that catching performance in children with DCD likely reflect a combination of errors in attending to visual information and movement organisation.

Comparing the catch composition, profitability and discard survival from different trammel net designs targeting common spiny lobster (Palinurus elephas) in a Mediterranean fishery.

In the Balearic Islands, different trammel net designs have been adopted to promote fisheries sustainability and reduce discards. Here, we compare the catch performance of three trammel net designs targeting the spiny lobster Palinurus elephas in terms of biomass, species composition and revenue from commercial catches and discards. Designs differ in the netting fiber type (standard polyfilament, PMF, or a new polyethylene multi-monofilament, MMF) and the use of a guarding net or greca, a mesh piece intended to reduce discards. Catches were surveyed by an on-board observer from 1,550 netting walls corresponding to 70 nets. The number of marketable species captured indicated that the lobster trammel net fishery has multiple targets, which contribute significantly to the total revenue. The discarded species ranged from habitat-forming species to elasmobranches, but the magnitude of gear-habitat interactions on the long term dynamics of benthos remains unclear. No relevant differences in revenue and weight of discards were detected after Bayesian analyses. However, the species composition of discards was different when using greca. Interestingly, high immediate survival was found for discarded undersized lobsters, while a seven day survival assessment, using captive observation, gave an asymptotic estimate of survival probability as 0.64 (95% CI [0.54–0.76]). Therefore, it is recommended that it would be beneficial for this stock if an exemption from the EU landing obligation regulation was sought for undersized lobsters in the Balearic trammel net fishery.

Influence of tow duration on catch performance of trawl survey in the Mediterranean Sea

The aim of this study was to assess the effect of tow duration on catch per unit of swept area (CPUE), trawl catch performance, and the proportion of the species caught in a trawl survey. Longer tows are expected to have a greater probability of catching species. An average of 26 species were caught in the first 30 minutes, whereas only about one additional species was caught in the next 30 minutes in longer tows. The shorter tows involved a decrement in catch weight for 11 of the 12 target species sampled, demonstrating that tow duration did affect catch per unit of swept area CPUE. The shorter tows were associated with a significant reduction of the overall CPUE in terms of weight of the main target species and of the total catch (circa 60%). The same strong reduction of around 70% was found in particular for European hake (Merluccius merluccius) and surmullet (Mullus spp) and 50% for Nephrops (Nephrops norvegicus). The shorter tows were less efficient in catching large-sized hake, surmullet, Nephrops, Atlantic horse mackerel (Trachurus trachurus), and poor cod (Trisopterus minutus), even though the difference was significant only for Nephrops. Regardless of the p-value statistic, these findings suggest that the continuity of survey time series would be severely impaired by changing tow duration. Further work is required to explore a way to reduce tow duration without reducing CPUE.

Comparative analysis of diet composition and its relation to morphological characteristics in juvenile fish of three lutjanid species in a Mexican Pacific coastal lagoon

ABSTRACT The main goal of this research was to investigate the differences in diet composition among three species of the genus Lutjanus inhabiting a coastal lagoon as juveniles. The working hypothesis was that these species feed on a common base of food resources and therefore, some niche overlap is present in terms of general diet composition. However, changes in the trophic niche with size and differences in some morphological traits among species explain observed differences in diet. Fish were collected during 42 sampling trips conducted regularly from February 2011 to January 2012 using several types of fishing gear. Total number of analyzed stomachs was 288 for Lutjanus argentiventris from 2.3 to 19.9 cm total length (TL); 178 for Lutjanus colorado ranging from 2.4 to 30.1 cm TL; and 183 for Lutjanus novemfasciatus with 1.2 to 20.0 cm TL. Results indicate that juveniles of all three lutjanid species share a general diet based on decapods and fishes. However, L. novemfasciatus has a more piscivorous habit, which can be explained by a more slender body shape and larger teeth, characteristics, which increase fish catching performance. Larger fish of all three species eat larger prey, which is consistent with the optimum foraging theory.

Comparison of the catch performance between traditional green jig and silver-white jig of squid jigging in Korea

Comparison of the catch performance between traditional green jig and silver-white jig of squid jigging in Korea

Predicting the effect of seine rope layout pattern and haul-in procedure on the effectiveness of demersal seine fishing: A Computer simulation-based approach.

Demersal Seining is an active fishing method applying two long seine ropes and a seine net. Demersal seining relies on fish responding to the seine rope as it moves during the fishing process. The seine ropes and net are deployed in a specific pattern encircling an area on the seabed. In some variants of demersal seining the haul-in procedure includes a towing phase where the fishing vessel moves forward before starting to winch in the seine ropes. The initial seine rope encircled area, the gradual change in it during the haul-in process and the fish's reaction to the moving seine ropes play an important role in the catch performance of demersal seine fishing. The current study investigates this subject by applying computer simulation models for demersal seine fishing. The demersal seine fishing is dynamic in nature and therefore a dynamic model, SeineSolver is applied for simulating the physical behaviour of the seine ropes during the fishing process. Information about the seine rope behaviour is used as input to another simulation tool, SeineFish that predicts the catch performance of the demersal seine fishing process. SeineFish implements a simple model for how fish at the seabed reacts to an approaching seine rope. Here, the SeineSolver and SeineFish tools are applied to investigate catching performance for a Norwegian demersal seine fishery targeting cod (Gadus morhua) in the coastal zone. The effect of seine rope layout pattern and the duration of the towing phase are investigated. Among the four different layout patterns investigated, the square layout pattern was predicted to perform best; catching 69%-86% more fish than would be obtained with the rectangular layout pattern. Inclusion of a towing phase in the fishing process was found to increase the catch performance for all layout patterns. For the square layout pattern, inclusion of a towing phase of 15 or 35 minutes increased the catch performance by respectively 37% and 48% compared to fishing without a towing phase. These results highlights the importance of the selected seine rope layout pattern and the duration of the towing phase when fishermen try to maximize the catch performance of their fishery. To our knowledge this is the first time the combination of models for the physical behaviour of seine ropes and for fish behaviour in response to seine rope movements have been applied to predict catch performance for demersal seining.

Effects of ipsilateral and crossed eye-hand dominance on catching performance in prepubescents

This study investigates the effects of ipsilateral and crossed hand-eye dominance on one and both hands catching performance (OHCP and BHCP) in participants aged 10 to 13 years. The combined groups including hand and eye dominance consisted of right handed-right eyed (RHRE), right handed-left eyed (RHLE), left handed-left eyed (LHLE) and left handed-right eyed (LHRE), respectively. In this study the mean values were only higher in the favor of LHLE females in left hand OHCP from 2 and 3 m distances. In other side, LHLE males had a higher mean values not only in left hand OHCP from 2 and 3 meters but also in the right hand OHCP from 3 meters. No significant difference was observed in BHCP among four groups in both genders. In conclusion, ipsilateral handeye dominance is an advantage for OHCP compared to cross dominance. Also left side had an advantage compare to the right side in OHCP.
 Keywords: Hand dominance; physical activity; gender.

The Effect of Intermittent Vest Cooling on Thermoregulation and Cardiovascular Strain in Baseball Catchers.

Bishop, SH, Szymanski, DJ, Ryan, GA, Herron, RL, and Bishop, PA. The effect of intermittent vest cooling on thermoregulation and cardiovascular strain in baseball catchers. J Strength Cond Res 31(8): 2060-2065, 2017-Baseball catchers are exposed to multiple physiological challenges while playing outside during the spring and summer months, many of which deal with recovery and thermoregulation. The purpose of this study was to investigate the effect of intermittent cooling on core temperature, cardiovascular strain, exertion, and recovery during a simulated catching performance in the heat. Six trained college-aged baseball catchers performed in a controlled, hot (35° C), and humid (25% relative humidity) environment in a counter-balanced, cross-over design. Ice vest cooling (VC) was used as a cooling modality and was compared with a control of no cooling (NC). Rectal temperature (Tre), heart rate (HR), rating of perceived exertion (RPE), and perceived recovery scale (PRS) were recorded before and after each simulated inning. All activities took place in a heat chamber, and each inning consisted of catchers receiving 12 pitches in their position followed by 6 minutes of recovery. Nine total innings were performed, and 27 total innings were performed with each of the 2 treatments. A significantly smaller mean Tre change was seen in VC when compared with NC (0.58 ± 0.2° C, 0.98 ± 0.2° C, p ≤ 0.01, respectively). Rating of perceived exertion was significantly lower and PRS was significantly improved for VC compared with NC (both p ≤ 0.05). Mean recovery HR during VC was significantly lower than NC in the fifth (VC = 84 ± 8 b·min, NC = 90 ± 9 b·min, p = 0.04), seventh (VC = 84 ± 3 b·min, NC = 92 ± 7 b·min, p = 0.02), and ninth (VC = 85 ± 7 b·min, NC = 93 ± 5 b·min, p = 0.01) innings. Heart rate during catching was significantly lower at the end of the VC trials when compared with NC (108 ± 16 b·min vs. 120 ± 19 b·min, p = 0.02, respectively). Vest cooling decreased heat strain, cardiovascular strain, and RPE while it improved perceived recovery in catchers over a simulated 3-game series performed in hot conditions.

A CFD study of the influence of turbulence on undercatch of precipitation gauges

The response of precipitation to turbulent fluctuations near gauges is studied using time-averaged (RANS) and unsteady (LES) turbulence modeling. Updrafting effects on catch performance are analyzed for unshielded and shielded gauges. The effective precipitation catchment area of the gauge for both wind-induced effects and snowflake characteristics is found to reduce significantly for small particles in high winds but can be partly recovered by shielding. The variation in the amount of precipitation caught is quantified for different free-stream wind speeds using LES and RANS. The fluctuations, captured with LES are analyzed to determine the local structure of eddies near the orifice plane. Wind-induced drag on precipitates are modeled for a wide range of particle Reynolds numbers from low speed Stokes flow condition to high speed flows with inertial effects. Results show noticeable effect of drag–force model on catch performance calculation of precipitation gauges with uncertainties of up to 40% in high winds and large snowflake sizes. Finally, particle–wall collision on the catch performance is studied for different restitution conditions. These simulations have differences of up to 5% in catch performance for large particle sizes in high winds, dependent on whether the particles undergo elastic or plastic collisions. Comparing RANS and LES results, turbulence fluctuations show a considerable influence on shielding performance degeneration at high winds. Double shielding the gauge can improve efficiency by maintaining a lower fluctuation-to-mean catch ratio as wind speed increases.

Engineering and catching performance of five netting materials in commercial prawn-trawl systems

High-strength netting trawls have less drag due to the opportunity to use thinner twine. In prawn/shrimp trawl systems, where large otter boards spread the trawls to high spread ratios, further substantial drag reduction should occur due to the reduced size of otter boards required. Here we conducted two comparative experiments with commercial prawn trawls made from five respective netting materials including standard polyethylene (PE), high tenacity PE and three examples of Ultra High Molecular Weight (UHMW) PE. In the first experiment, a sequence of paired comparisons of engineering performance (drag and spread) was undertaken across all trawls individually connected to one of three pair of different size otter boards; in all cases codends were left open to avoid catch size confounding the measurements. In the second experiment, catch and selectivity performances were assessed by towing the five trawls simultaneously in a five-rig system, with location in the system randomly varied. The trawl-board combination with the best engineering performance for each high-strength material produced a range of drag reduction compared to the best combination for the standard PE trawl: ∼12% for high tenacity PE and ∼19–21% for the three UHMW PE trawls. The high-strength netting trawls caught larger prawns compared to the standard PE trawl, possibly due to (i) increased twine flexibility allowing smaller prawns to escape, and (ii) greater flow of water through the trawl causing increased catch efficiency for larger, more mobile prawns. A strong negative result was the large amount of bycatch for most high-strength netting trawls—it was concluded that this was driven in part by low fishing line tension, exacerbated by higher operating spread ratio. Some evidence was obtained that this could be mitigated by applying layback to the headline.

Artificial lights improve the catchability of snow crab (Chionoecetes opilio) traps

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.