Catch Damage Research Articles

Socioeconomic impacts of Australian redclaw crayfish Cherax quadricarinatus in Lake Kariba

The rapidly spreading Australian red claw crayfish Cherax quadricarinatus in the Zambezi Basin is a cause for concern considering its potential impacts. The assessment of the impacts of C. quadricarinatus is critical for the prioritisation of policy and management actions in Africa where literature on impacts of C. quadricarinatus is generally scant. We quantified the socioeconomic impacts conferred by C. quadricarinatus on artisanal gillnetting fishery in Lake Kariba to validate anecdotal fisher reports regarding crayfish damage to fish catch on static gillnets. From the catch assessments with registered fishers, fish catch composition, catch per unit effort (CPUE), crayfish entangled on gillnets CPUE, damaged fish CPUE, and damaged areas of the fish were recorded. Basin 2 had significantly higher CPUE with respect to fish catch and crayfish, as well as catch damage, compared to other basins. Damage by crayfish on fish was recorded in all the basins except in Basin 5. There was no correlation between number of crayfish bycatch and fish catch damage. The most frequently affected species was Oreochromis niloticus. On all fish species, eyes, guts and the tail were the frequently damaged parts. Due to C. quadricarinatus damage, fishers are losing 212 tonnes per year which translates to US$ 512 352.92 in Lake Kariba. Damage losses are particularly high when the total income per household in the region, which is mainly contributed by fishing, is considered. The lack of damage in Basin 5 is likely due to fishers developing adaptive new techniques which are less likely to be affected by crayfish. This study is the first in Africa to quantify the socio-economic losses due to crayfish in the field, and the first globally to derive observed costs for C. quadricarinatus. Data from this study have huge conservation and management implications, as crayfish threaten food security as well as incur personal losses to fishers via damage-related costs.

Interactions between common bottlenose dolphins (Tursiops truncatus) and the artisanal fishery in Asinara Island National Park (Sardinia): assessment of catch damage and economic loss

In 1999, the Italian Central Institute for Applied Marine Research (ICRAM), in response to reports made by local fisheries, began a study into the interactions between common bottlenose dolphins (Tursiops truncatus) and the artisanal fishery in the Asinara Island National Park (Sardinia). Using onboard observers, fishing boat surveys were carried out to determine the frequency of interactions, variations in the catch of target species and damage to two different types of trammel net caused by dolphins. Interactions occurred primarily with trammel nets targetting striped red mullet (Mullus surmuletus; the less valuable peacock wrasse, Simphodus tinca, was also caught). Interactions also occurred with trammel nets set for lobster (Palinurus elephas), cuttlefish (Sepia spp.) and scorpionfish (Scorpaena spp.), but these were considered negligible. The target species, catch and damage inflicted on the catch was recorded, both in the presence and absence of dolphins, in an effort to ascertain associated damage and economic cost. Loss of catch was found to be significant only in the case of nets deployed during the red striped mullet fishing season. Although the level of interaction was high relative to the narrow red striped mullet fishery season, the overall economic impact on the fishing community was found to be modest. The presence and regulations of the national park area may provide an opportunity for investigating mitigation activities compatible with both cetacean conservation and the maintenance of the traditional fisheries.

Fishers’ Perception on the Interaction between Dolphins and Fishing Activities in Italian and Croatian Waters

Interactions between fishing and dolphins can be detrimental, since on one hand dolphins can be lethally entangled by nets and trawls, and on the other dolphins can predate fish caught by nets. For dolphins, this interaction can be dangerous as they can be wounded or accidentally killed; for fishers, the predation of their catch results in economic losses due to reduced quantity and/or quality of catches and damage to fishing gear. During July and November 2020, we surveyed the “dolphin–fisheries conflict” through compiling 209 fisher interviews from nine locations in Italy and Croatia. Fishers mentioned the common bottlenose dolphin (Tursiops truncatus) as the species primarily interacting with fishing, with the major issue being catch damage by predation. The interaction probability varied among gears and seasons, with some fishing activities (e.g., passive nets) more affected than others (e.g., bottom trawls), especially in terms of economic loss (1000–10,000 €/year on average). More than 70% of the fishers claimed that dolphin populations have increased over the last 10 years, in different degrees and based on different areas. Dolphin bycatch rates are generally low; however, 34.6% of respondents reported having captured at least one dolphin during their career. The fishers’ attitude towards acoustic deterrents (“pingers”) as a mitigation measure revealed that few of them were aware of these devices or were using them.

Questionnaire and experimental surveys show that dolphins cause substantial losses to a gillnet fishery in the eastern Mediterranean Sea

AbstractCommon bottlenose dolphins (Tursiops truncatus) are known to depredate fishing gear, resulting in damage to the catch and/or the gear itself. The extent of this damage and estimated financial loss varies between areas, métiers, and survey methods. We quantified losses due to bottlenose dolphin depredation in a coastal gillnet fishery in the Thermaikos Gulf, Greece, in terms of CPUE reduction, catch damage, and gear damage. Experimental fishing effort was carried out over two seasons (2020 and 2021), along with concurrent questionnaire surveys over the second season (2021). Depredation frequency (∼35%) and CPUE changes due to depredation (a significant decrease of 45–50%) were similar for both sampling schemes. The number of damaged fish in experimental hauls increased significantly with dolphin depredation, but did not fully account for the sizeable loss in marketable catch, indicating that large numbers of fish were removed from the nets entirely. Damage to experimental nets increased with dolphin presence and group size, with an average of 0.59% of net surface area damaged per depredation event. Both datasets point to annual economic losses of over €5000 per vessel in this fishery, while the similarity between direct observations and self-reported losses highlights the usefulness of frequent questionnaire surveys.

Effect of the T90-codend on the catch quality of cod (Gadus morhua) compared to the conventional codend configuration in the Barents Sea bottom trawl fishery

The aim of this study was to compare the catch quality of Northeast Atlantic cod (Gadus morhua) in the Barents Sea bottom trawl fishery caught using the conventional configuration (a sorting grid followed by a diamond mesh (T0) codend) and a T90° turned mesh codend (T90) without a grid. Twenty hauls were conducted, consisting of 10 hauls with the conventional configuration and 10 hauls with the T90-codend. The catch quality was assessed using the catch-damages-index (CDI) and a newly developed method using VIS/NIR hyperspectral imaging to estimate the residual blood abundances in the fish muscle. The probability of obtaining fish with no damage was 23.4% (CI: 16.3–31.1%) for cod captured by the conventional configuration, and 21.2% (CI: 15.4–27.2%) for cod captured by the T90-codend. The average blood abundance (in arbitrary unit) was 0.86 (CI: 0.85–0.87) for cod captured by the conventional configuration and 0.88 (CI: 0.87–0.88) for cod captured by the T90-codend. Catch quality of the hauls obtained using the two gears did not differ significantly in terms of catch damage or residual blood levels in the cod. Hence, this study demonstrated that T90-codends do not compromise catch quality compared to regular diamond meshed codends.

Sensory evaluation of fresh/frozen mackerel products: A review

Mackerel has received considerable attention in the global food market as one of the most important pelagic commercial fish species. The quality of mackerel is influenced by species, season, fishing area, nutritional status, catching method, handling, and storage. Due to the mackerel's perishability, its quality is mainly measured by sensory procedures. Although considerable effort has been made to explore quick and reliable quality analysis, developing a practical and scientific sensory evaluation of mackerel has been an active ongoing study area to meet the quality evaluation demand of the industry. Different sensory evaluation methods have been used to assess the mackerel fish quality, including Palatability and Spoilage test, Torry scheme, EU scheme, Quality Index Method, Catch damage index and Processed fish damage index, Affective test, Discriminative test, and Descriptive test. Each method has its strength and weakness. Despite mackerel sensory evaluation protocols having undergone partial harmonization, specific sample process needs to be carefully followed to minimize the change during sample preparation. This review summarizes the sensory evaluation methods in mackerel research, the factors affecting sensory evaluation, and then updates the latest advances in mackerel sensory evaluation and offers guidance for presenting its application in the mackerel chain. Also, each technique's advantages and limitations are discussed. In our opinion, the future trends for sensory evaluation of mackerel should be consumer-centric.

Measures for co-existence between seals and coastal large-scale salmon set net fisheries: Mitigation of catch damage by the use of rope grid

In recent decades, conflict between Kuril harbor seals (Phoca vitulina stejnegeri) and local fisheries have become a serious problem in Hokkaido, northern Japan. Catch damage in large-scale salmon set nets may be mitigated by attaching a rope grid to set net funnels. We investigated the effectiveness of different rope grids on catch damage caused by seals, and evaluated hidden impacts on catch caused by the seals using an underwater camera for observation of seal and salmon behavior coupled with on-board observations of catch and catch damage. The rate of seal prevention was highest for rope grid with 20 cm × 20 cm spacing (97.5 %). The percentage of catch damage in the set net with this rope grid was significantly lower than that for the set net with other rope grid which was easy to enter for seals. We concluded that it is effective to attach an appropriate rope grid to set nets to prevent seals from entering fish bags and to ensure salmon catch amounts. The existence of “hidden damage” was quantitatively revealed via the underwater observation of seals removing salmon from the fish bag, and by comparing the number of salmon between underwater observation and on-board observation.

Effect of gear design on catch damage on cod (Gadus morhua) in the Barents Sea demersal trawl fishery

Damage incurred during the catch process is an indicator of the overall quality of fish and fish welfare. Because catch quality is difficult to improve once it has deteriorated, it is important to preserve quality during the catch process. Atlantic cod (Gadus morhua) is the most important species in the Barents Sea bottom trawl fishery. Bottom trawling is a non-benign fishing method, and it is therefore considered important to reduce damage imparted to fish during capture, and subsequently improve catch quality and fish welfare. In the present study, the levels of damage on cod captured with a new gear design were assessed in the Barents Sea bottom trawl fishery. Furthermore, this study investigated to what extent the compulsory sorting grid and diamond mesh codend configuration employed in the fishery is responsible for the damage incurred by cod during the capture process. In total, 750 cod captured over 25 hauls were evaluated for catch damage (marks, ecchymosis, exsanguination, and scale loss). The results showed that substituting the grid and codend configuration with a four-panel selective knotless section followed by a gentle codend increased the probability of cod having no catch damage by 6.00% (CI: 0.6%–11.41%). Moreover, the gentle codend led to a significant reduction in the severity of all catch damage categories.

Sequential codend improves quality of trawl-caught cod.

Trawl-caught fish are frequently associated with deteriorated catch quality. This study presents a new dual sequential codend concept with the aim of improving the quality of trawl-caught fish by minimizing the frequency and severity of catch damage. During towing, the fish are retained in an anterior codend segment with the legislated mesh size. A quality improving codend segment, is attached to the aft part of the first codend segment. Its entrance is closed during the towing phase and opened at a predefined depth during haul-back. Comparing the quality of cod (Gadus morhua L.) retained in the sequential codend with cod caught in a conventional codend, demonstrated a significant improvement in the catch quality, i.e. reduction in catch damages. Cod caught in a conventional codend had only a 3.6% probability of being without visually detectable catch damage. The probability for catching cod without catch damage was five times higher when using the dual sequential codend. Furthermore, cod caught in the sequential codend had a significantly reduced probability of incurring specific catch damage, such as gear marks, poor exsanguination, ecchymosis, and skin abrasions.

Acoustically monitoring the Hawai‘i longline fishery for interactions with false killer whales

False killer whales (Pseudorca crassidens) feed primarily on several species of large pelagic fish, species that are also targeted by the Hawai‘i-permitted commercial deep-set longline fishery. False killer whales have been known to approach fishing lines in an attempt to procure bait or catch from the lines, a behavior known as depredation. This behavior can lead to the hooking or entanglement of an animal, which currently exceeds sustainable levels for pelagic false killer whales in Hawai‘i. Passive acoustic monitoring (PAM) was used to record false killer whales near longline fishing gear to investigate the timing, rate, and spatial extent of false killer whale occurrence. Acoustic data were collected using small autonomous recorders modified for deployment on the mainline of longline fishing gear. A total of 90 fishing sets were acoustically monitored in 2013 and 2014 on a chartered longline vessel using up to five acoustic recorders deployed throughout the fishing gear. Of the 102 odontocete click and/or whistle bouts detected on 55 sets, 26 bouts detected on 19 different fishing sets were classified as false killer whales with high or medium confidence based on either whistle classification, click classification, or both. The timing of false killer whale acoustic presence near the gear was related to the timing of fishing activities, with 57% of the false killer whale bouts occurring while gear was being hauled, with 50% of those bouts occurring during the first third of the haul. During three fishing sets, false killer whales were detected on more than one recorder, and in all cases the whales were recorded on instruments farther from the fishing vessel as the haul proceeded. Only three of the 19 sets with acoustically-confirmed false killer whale presence showed signs of bait or catch damage by marine mammals, which may relate to the difficulty of reporting depredation. PAM has proven to be a relatively inexpensive and efficient method for monitoring the Hawai‘i longline fishery for interactions with false killer whales.

Testing the effect of soak time on catch damage in a coastal gillnetter and the consequences on processed fish quality

This study aims at testing how to improve catch quality aboard a coastal gillnetter by looking at an easily controllable parameter known to have an effect on the degree of fish damage, soak time, and investigating if the registered damages on whole fish have an effect on processed products such as fillets. Plaice (Pleuronectes platessa) was captured with commercial gillnets soaked for 12 and 24 hours. Damages were assessed using semi-quantitative indices of individual fish condition gathered in a Catch-damage-index for onboard fish and a Processed fish-damage-index for whole, skinned and filleted plaice processed at a land-based factory. Cumulative link mixed modelling allowed the estimation of the size of effects. Damage in fish was significantly more likely for longer soak times but effects were comparable to those of fish length and between-sets, making a change in soak time not so substantial for improving plaice quality in coastal gillnetting. Damage in fish was significantly more likely for whole than filleted fish, but there was substantial heterogeneity among fish. Severe damage in whole fish may not matter in filleted fish whereas some damage may only be visible at the fillet level.

Pumping of mackerel (Scomber scombrus) onboard purse seiners, the effect on mortality, catch damage and fillet quality

Differences in the mortality, catch damage, and fillet quality of mackerel pumped either from the seine directly onboard the catching vessel or transferred at sea to a secondary vessel were explored. Three studies were performed on commercial vessels, both purse seiners and coastal seiners, during the catching season in September and October 2012–2014. Most of the fish died after 20 to 60min due to the duration of the crowding time. There was a significantly higher survival rate for the fish that were pumped to the main vessel due to shorter crowding time compared to the fish that were pumped to the secondary vessel, with an average survival rate of 53.4% ​​versus 23.9% The mackerel caught with the secondary vessel in 2014 had a significantly higher proportion of catch damage and discolorations compared to the fish caught with the main purse seine in 2014, and coastal vessels in 2012 and 2013. For the experiment in 2014, a sensor fish was developed with the purpose of registering acceleration forces (g-forces) during pumping. The results from the sensor fish revealed that more strain/g-forces (29%) were exerted on the fish pumped to the secondary vessel as compared with the main vessel. This is likely to be the result of several factors: (a) the pump speed was higher (30%), (b) more fish were processed, and (c) the tubing system extension of 50m created a “rollercoaster” course for the fish. The quality of the fillets was good overall, but with some differences in gaping scores between the main and secondary vessels after storage onboard.

Quality assessment of Atlantic cod ( Gadus morhua) caught by longlining and trawling at the same time and location

The quality of Atlantic cod from one trawl catch and one longline catch, caught at the same time and location, was assessed and compared. In addition, the effect of ice storage in 7 days on quality parameters was investigated. No differences between the cod from the two catches were observed on microbial activity and drip loss. Trawl caught cod had decreased pH and increased TMA compared to longlined cod. Catch Damage Index showed that trawling gave increased damages compared to longlining, where trawling resulted in poor bleeding and bruises, while longlining resulted in gaffing damages. Both color and sensory analyses confirmed the poor bleeding of trawl caught cod. In addition, the longline caught cod had increased overall sensory quality and increased lightness. Water holding capacity was decreased in trawled cod compared to longlined cod together with increased protein denaturation measured by differential scanning calorimetry. Texture analysis showed increased firmness in longlined cod. Cod loins stored on ice for 7 days encountered decreased quality attributes evaluated by sensory methods, firmness, water holding capacity and lightness, while microbial growth, pH and protein denaturation of the loin increased. In this study, the catch of Atlantic cod caught by longline had a better overall quality compared to the catch of cod caught by trawl.

Mass Trapping of <I>Prays nephelomima</I> (Lepidoptera: Yponomeutidae) in Citrus Orchards: Optimizing Trap Design and Density

The moth Prays nephelomima (Meirick) (Lepidoptera: Yponomeutidae) is a significant pest of citrus (Citrus spp.), and the recent identification of the female sex pheromone has enabled new direct control tactics to be considered. Six trap designs were compared for suitability in mass trapping, and Pherocon III delta traps were chosen to further evaluate mass trapping. A mass trapping field trial was carried out at five lemon, Citrus limon L., orchards to determine the effect of trap density on catch and rind spot damage on fruit. One plot (0.33-1.0 ha) of each of the five trap density treatments (3, 10, 30, 100, and 300 traps/ha) were operated at each orchard over 12 wk. Catch per trap was reduced as trap density increased and a mean of 12,000 and 16,000 males per ha were killed at the trap densities of 100 and 300 traps per ha, respectively. Increased trap density reduced the percentage of flowers infested with P. nephelomima larvae and reduced the number of moths emerging from flowers. The incidence of rindspot damage on fruit decreased from 45 to 16% as the density of traps increased from 3 to 100 traps per ha. Incidence (percentage of fruit with rindspot) and severity (number of rindspots per fruit) was similar at 100 and 300 traps per ha, indicating that the optimal trap density for reducing rindspot damage is likely to be between 30 and 100 traps per ha. Prospects for converting mass trapping to a lure and kill system are discussed.

Catch Composition and Damage Incurred to Crabs Discarded from the Eastern Ligurian Sea “rapido” Trawl Fishery

Catch Composition and Damage Incurred to Crabs Discarded from the Eastern Ligurian Sea “rapido” Trawl Fishery

Acoustic harassment devices reduce seal interaction in the Baltic salmon-trap, net fishery

Abstract Acoustic harassment devices (AHDs) were deployed at salmon-trap nets in the Baltic Sea to reduce gear and catch damage by grey seals (Halichoerus grypus). The AHDs emitted pulses of 250–500-ms duration, worked at a frequency of 15 kHz, and a source level of 179 dB re 1 μPa rms at 1 m. AHDs were deployed during three consecutive fishing seasons. Catches were significantly higher in traps with AHDs (25.5 kg d−1) than in controls (12.0 kg d−1), and catch damage was less (3.5 vs. 6.7 kg d−1). These results persisted over and between fishing seasons, but late in the season damage to the catches was common also in traps with AHDs. This study shows that the AHD may be a complementary mitigation tool in the seal–fishery conflict in certain types of fisheries, even though it is technically demanding, and for environmental reasons should be used with great care.

Temporal and regional patterns in seal-induced catch and gear damage in the coastal trap-net fishery in the northern Baltic Sea: effect of netting material on damage

Seal-induced damage in the traditional trap-net fishery increased dramatically during the 1990s in the northern Baltic Sea. Most damage is induced by a rapidly growing grey seal (Halichoerus grypus) population. We evaluated seal damage in the coastal trap-net fishery of the Gulf of Bothnia, where different gear constructions and netting materials are used. A total of 72 commercial fishermen with 136 trap-nets were involved in the study. Catch and gear-damage observations made by fishermen were consistent with our own. The largest catch losses of salmon (Salmo salar) were recorded in the Bothnian Sea, where seals damaged at least 37% of salmon catch (by number). In other regions, losses were notably smaller, at between 3 and 9%. The number of salmon caught in a trap on any one occasion correlated significantly with the number of damaged salmon. However, the more salmon were present in a trap, the smaller was the proportion damaged by seals. Observed catch losses in the whitefish (Coregonus sp.) fishery varied between regions from 5 to 7%. Gear damage was observed in 2–15% of trap-net emptyings, depending largely on region. The extent of gear damage followed the trend of catch damage in each region. Fish entanglement in trap-nets increased the amount of gear damage. The type of netting material significantly affected gear-damage frequencies and salmon entanglement. Seal-induced catch and gear damage could be reduced by gear modification and operational changes. The choice of suitable netting materials and the development of seal-safe fish-bags are essential in protecting the gear and catch from seals. © 2005 Elsevier B.V. All rights reserved.

Mitigation of seal-induced damage in salmon and whitefish trapnet fisheries by modification of the fish bag

Abstract During the past decade, seal-induced gear and catch damage has increased dramatically in the Baltic Sea. The problems are most severe in the coastal trapnet fisheries for salmon (Salmo salar) and whitefish (Coregonus lavaretus), where grey seals (Halichoerus grypus) in particular frequently visit the traps. There is an acute need for gear modifications and other solutions that can prevent seals from entering the fish bag of the traps. Modifications that have been tested in Finland include a wire grid installed in the funnel of the trap and a fish bag made of extra-strong netting material. In comparative fishing experiments conducted in 2001 in the Gulf of Finland the grid was made of 2-mm steel wires with 175-mm spacing. The average undamaged salmon catch per haul in the fish bag of modified trapnets was significantly higher (70%) than that of traditional traps (Mann–Whitney, p < 0.01). In the whitefish experiments, the average undamaged catch of whitefish per haul was 16% higher in modified trapnets than in traditional traps, but the difference was not significant (Mann–Whitney, p > 0.05). These results indicate that the wire grid did not prevent fish from swimming into the fish bag. Experiments also suggest that the wire grid and the extra-strong netting prevented seals from entering the bag. However, on some occasions seals were able to tear the fish through the netting. Underwater observations confirmed that the wire grid kept adult seals outside the bag while salmon and whitefish could be seen entering through the grid into the bag.

Comparisons of Two Trapping Methods for Hylobius pales (Coleoptera: Curculionidae) in Virginia

The pales weevil, Hylobius pales (Herbst), is a major regeneration pest of Christmas tree plantations in the eastern United States, where traditional control measures include the use of highly toxic insecticides. The development of an effective, easily implemented sampling strategy to detect when serious infestations are imminent is highly desirable for reducing these preventative insecticide applications. Methods were evaluated for trapping walking H. pales under 3 vegetation management treatments in Christmas tree plantations and for their potential to forecast seedling damage. Standard pit traps baited with natural host material and synthetic volatiles caught significantly more H. pales than polyvinyl chloride (PVC) pitfall traps baited with synthetic volatiles alone. No gender differences were observed in response to the trap treatments. No differences in catch were observed between stationary traps and traps rotated biweekly to different locations within each plot. Vegetation management had no significant effect on trap catch. However, H. pales fed on a significantly higher proportion of eastern white pine seedlings, Pinus strobus L., in plots not managed for competing vegetation than in herbicide-treated plots. The data suggested a strong linear relationship between catch and seedling damage; these variables were significantly correlated in 1995, but not in 1994. However, one must be cautious because this regression was based solely on 4 data points. The seasonal occurrence of H. pales in Virginia Christmas tree plantations is reviewed in detail. Our results suggest we must rely on the use of pit traps for monitoring weevil populations in Virginia until an appropriate system for implementing the PVC pitfall trap is developed.