Net Fishery Research Articles

The effects of two different net modifications on reducing discards in the trammel net fishery for prawn in Mersin Bay

The discarded species caught in prawn trammel nets damage the nets and cause a serious labor loss problem for fishers. In the present study, a 15 cm high greenhouse plastic film and a greenhouse shade cloth net were fitted between the lower parts of the nets and the lead collars to reduce discards in the trammel net fishery. The modified nets were tested in Mersin Bay with twenty-one fishing operations between September and December 2021. The results showed that, compared to commercial trammel nets, the nets equipped with greenhouse plastic film and greenhouse shade cloth did not significantly reduce the catch of the target species green tiger prawn (Penaeus semisulcatus). However, the total number of discards significantly decreased. The discard rates in the commercial net, greenhouse plastic film net, and greenhouse shade cloth net were 45%, 26%, and 22%, respectively. Furthermore, when the incomes from the nets’ hauls were calculated, the net equipped with greenhouse garden film and the net equipped with greenhouse shade cloth generated 24.77% and 14.41% more profit than the commercial net, respectively.

Comparison of physical properties and fishing performance between biodegradable PLA and conventional PA trammel nets in grey mullet (Mugil cephalus) and red-lip mullet (Liza haematocheila) fishery

Marine plastic pollution and continuous capture of marine animals, so-called “ghost fishing”, by abandoned, lost, or otherwise discarded fishing gear (ALDFG) are global concerns. This study investigated whether biodegradable polylactic acid (PLA) monofilaments can be used to replace conventionally used non-biodegradable polyamide (PA) in trammel net fishery for limiting ALDFG associated effects. It evaluated the physical properties of PLA and PA monofilaments and compared fishing performance of PLA and PA trammel nets in a commercial mullet fishery in the Yellow Sea, China. Although PA monofilament exhibited superior physical properties, no significant differences in catch efficiency between PA and PLA trammel nets were observed. Fish of both species were mainly captured by pocketing which can further explain observed similar catch efficiency. These initial results suggest a potential for applying biodegradable materials in trammel net fisheries. Therefore, further long-term testing is encouraged to investigate whether this promising performance is persistent over long-term.

Spatiotemporal variations and influential factors affecting reproductive dynamics of Pacific saury in the Northwest Pacific during fishing season.

This study examined the spatial and monthly variations in reproductive dynamics of Pacific saury collected in the high sea (40°N-49°N, 149°E-168°E) of the northwestern Pacific during the fishing season of the Taiwanese stick-held dip-net fisheries (July-November) from 2018 to 2019. Generalized additive mixed-effects models (GAMMs) were applied to explore the relationship between the probability of maturing and spawning occurrence (PMOS ) and the explanatory variables (month, body length, sea-surface temperature [SST] as fixed effects, and fishing set as a random effect) for the age 0 and age 1 fish, respectively. In addition, the impact of the geographical difference in growth rates of age 0 fish, quantified as the radius of the otolith annual ring, on the PMOS of age 1 fish was explored in the GAMMs. Results showed that the mean values of the condition factor (CF) varied by months, and higher mean CFs were observed north of 45°N. However, the mean values of the gonado-somatic index did not show a clear spatiotemporal pattern. The spatial distribution of the ovarian maturation states revealed that the spawning ground of Pacific saury during July-November was broader than that previously known and had partly overlapped with the high-sea fishing ground. The best GAMM showed that the predicted PMOS of the age 0 fish were generally low (mean = 19%, standard deviation [SD] = 10%) and tended to increase with increasing body length. In contrast, the predicted PMOS were relatively higher (mean = 37%, SD = 10%) for the age 1 fish and increased with increasing SST and decreasing latitude. Two candidate GAMMs, which are equally supported as the best model (ΔAIC < 2), provide evidence that a higher growth rate of age 0 fish may result in higher reproductive activity in age 1 fish. This is one of few studies focusing on the reproductive dynamics of Pacific saury during the fishing season; current limitations, future directions, and conservation implications were discussed.

An Innovative Designed Velocimeter Application for Set Net Fishery

This article is aimed at the problems encountered by the fishing ground of set nets in Taiwan when the set net operators need to work when the weather is bad at sea. We developed a velocimeter that can be placed in the ocean for a long time and change sensing directions with the flow direction. The self-designed velocimeter has advantages, such as simple operation, low cost, and easy maintenance. With wireless monitoring and an early warning system, it can monitor current velocity, flow direction, sea temperature, and displacement. The data is transmitted back to the operator through the radio transmission module as a basis for dispatching personnel to go out to sea for fishing. To prevent the set net from drifting into the open sea due to bad weather, a GPS module is used to monitor the current location of the set net. If the waves wash away the set net, the warning signal can be received the first time to prevent the floating set net from endangering the safety of ship navigation and the survival of marine life. This innovative technology aligns with SDG 14, which aims to “conserve and sustainably use the oceans, seas, and marine resources for sustainable development”.

A study on species composition and bycatch status of fishes by a three-side fyke net fisheries in Asanho Lake and Chungjuho Lake

A study on species composition and bycatch status of fishes by a three-side fyke net fisheries in Asanho Lake and Chungjuho Lake

Growth and exploitation of Salema Sarpa salpa (Linnaeus, 1758) (Sparidae) in the North Aegean Sea, Türkiye

Salema, Sarpa salpa (Linnaeus, 1758), is a herbivorous fish species of the family Sparidae. It is an important predator of benthic algae, especially seagrass Posidonia oceanica. Due to excessive herbivorous behaviour, ecological importance becomes more significant than economical value. Thus, the aim of this study was to contribute scientific knowledge of Salema stock distributed around North Aegean Sea, Turkey with reveal age structure, growth, mortality, and exploitation rates. For this purpose, a total of 412 specimens, varied between 10.2 cm and 38.0 cm TL in length were obtained by commercial gill net fisheries monthly. The length-weight relationship (LWRs) was calculated as W=0.01898*TL2.883 (r2=0.97), and growth type was determined as negative allometric in all sexes. The von Bertalanffy growth parameters were calculated as L∞=41.6 cm, K=0.21 y-1, and t0=-1.50 y, and the total mortality (Z), natural mortality (M), fishing mortality (F), and exploitation rate (E) were calculated as 2.04, 0.44, 0.81, and 0.65, respectively. The fishing mortality optimum reference point (Fopt), fishing mortality limit reference point (Flim), optimum exploitation rate (Eopt) and the length where the maximum yield can be obtained (Lopt) were calculated as Fopt=1.02, Flim=1.36, Eopt=0.44, and Lopt=28.6, respectively.

Evaluating dolphin damage in trammel net fisheries in the Valencia region: Insights to improve management

Interactions between dolphins and trammel net fisheries have been described in the Mediterranean Sea as having negative consequences for both cetaceans and fishers. There is a need for studies that evaluate the economic costs caused by dolphins feeding from entangled fishes in trammel nets since most cetacean species involved in these interactions are endangered. This study aims to evaluate the economic impact of the interaction between dolphins and trammel nets fisheries in the coastal waters of the Valencian region in the western Mediterranean Sea. We conducted at-port visual inspections of nets from April 2018 to March 2019, which included 1,849 fishing operations with trammel nets, and we recorded damages to the net and catch and the value of the fishery. Thirty-two interactions were detected during the year of the study. The only observed species interacting was the common bottlenose dolphin. No bycatch of dolphins was reported. The interactions have been impacted seasonally and most of them took place in February and March. There were no significant differences in catch when comparing sets with and without depredation or damage in nets due to depredation by dolphins. Also on average, no differences were found in the value of the catch when comparing sets with or without damage caused by dolphins. The main cost to the fisher was the cost of repairing the nets. The estimated financial loss per vessel and year was €556 (95%CI: €303–€809). This represents less than 1% of the total yearly income of each vessel in our area. We suggest implementing tools to economically compensate artisanal vessels for any damage caused by dolphins in order to avoid increasing the hostile feeling of fishers towards dolphins and to apply conservation measures to protect this cetacean species.

A web-based numerical model for sustainable management of Lake Batur, Bali: Preliminary results

Lake Batur is one of The National Priority Lakes according to President Regulation Number 60/2021 with the target of restoring water quality through the pollution control program for floating net fishery (FNF), agriculture, and other anthropogenic sources around the watershed. The regulation also states several internal measures designed to restore the lake’s water quality. Unfortunately, detailed information on pollution control priorities, the amount that must be controlled for water quality improvements to be visible, and the effectiveness of internal restoration efforts have yet to be obtained. This can hinder the lake restoration process and, furthermore, its sustainable management. This study aimed to develop a web-based numerical model as an open-source web-service for guiding restoration in Lake Batur. It is accessible via the interactive graphical user interface (GUI) running in a standard web browser and includes tools of varying complexity. The platform provides the user with features to set up some parameters, run and analyze the numerical water quality, and the possibility to set up, run and compare various lake management scenarios. The preliminary results show that the model was able to represent existing daily water quality dynamics. Hopefully, the model can be used as a tool for lake restoration and as a part of sustainable lake management.

Estimation of selectivity parameters for target and bycatch fishes of the trammel net fisheries in the northern Aegean Sea (eastern Mediterranean Sea)

The size selectivity of trammel nets was investigated in the northern Aegean Sea using 10 different inner-panel mesh sizes ranging from 16 to 70 mm nominal mesh size (bar length). Selectivity estimates were made for the eight most abundant target and bycatch fish species, namely black scorpionfish, Scorpaena porcus Linnaeus, 1758; annular seabream, Diplodus annularis (Linnaeus, 1758); red mullet, Mullus barbatus Linnaeus, 1758; surmullet, Mullus surmuletus Linnaeus, 1758; round sardinella, Sardinella aurita Valenciennes, 1847; European hake, Merluccius merluccius (Linnaeus, 1758); greater weever, Trachinus draco Linnaeus, 1758; and blotched picarel, Spicara flexuosum Rafinesque, 1810, which accounted for 51.5% by number and 42.7% by weight of the fish caught with trammel nets in the sea trials. The SELECT method was used to estimate the selectivity parameters. Five different selectivity functions (i.e., normal scale, normal location, gamma, log-normal, and bi-normal) were applied with the bi-normal function providing the best fit as it had the lowest deviance value for all species and the lowest values for the dispersion parameter ( D /df). The mesh size of 16 mm in most of the cases retained specimens below the size at first maturity ( L m ). The mesh size of 19 mm seems more appropriate for red mullet, surmullet, and blotched picarel, the mesh size of 22 mm for annular seabream and round sardinella, while for European hake and black scorpionfish, the mesh size larger than 26 mm would be more appropriate.

SFA를 이용한 근해어업의 온실가스 배출 효율성 및 감축잠재량 추정

The purpose of this study is to estimate greenhouse gas(GHG) emission efficiency(GEE) and GHG mitigation potential(GMP) of offshore fisheries in preparation for carbon neutral and negative promotion in the ocean and fisheries sector, and to suggest policy improvements related to GHG mitigation. To this end, this study used stochastic frontier analysis(SFA) considering exogenous determinants of GHG emission inefficiency. As a result, the GEE of fleet and drag net fisheries with high fuel cost and vessel age was lower than other fisheries. In addition, the GMP and mitigation ratio of large purse seine, large pair trawl, large otter trawl, and anchovy drag net were higher than those of other fisheries. Lastly, as policy improvements to reduce GHG emission from offshore fisheries, fleet size reduction, development of low-energy used fishing gear, easing of conditions for participation in fishing vessel modernization projects, revising laws to supply eco-friendly fishing vessel, and improvement of the tax-free petroleum supply system were proposed.

Effect of Codend Design and Mesh Size on the Size Selectivity and Exploitation Pattern of Three Commercial Fish in Stow Net Fishery of the Yellow Sea, China

To address the issue of minimum mesh size regulations of the stow net fishery for croaker species, we tested and compared the size selectivity and exploitation pattern for diamond- and square-mesh codends with mesh sizes 35, 45 and 55 mm for little yellow croaker (Larimichthys polyactis), silver croaker (Pennahia argentata), and flower croaker (Nibea albiflora) in the Yellow Sea, China. Our results showed that the legal codend (35 mm diamond-mesh) was inadequate to protect the juvenile croaker species because more than 75% of undersized individuals were retained, and the discard ratios were as high as approximately 60%. Irrespective of mesh shape, increasing the codend mesh sizes could significantly improve the size selectivity and exploitation pattern of croaker species. Between codends with the same mesh size, the square-mesh codends had higher size selectivity than diamond-mesh codends. Based on results, the 55 mm square-mesh codend was recommended for rational exploitation of croaker stocks. This study can provide feasibility and insight for the enforcement and reform of management strategies for sustainable fishing in Chinese stow net fisheries.

Gill Net Fishery Development Strategy in Cilacap Districk, Central Java Province, Indonesia

Capture fisheries require resource management to optimize fishing activities, followed by efforts to maintain ecosystems and preserve fish resources as catch targets from the threats of degradation and extinction. For that a descriptive research was conducted from January-July 2021 on stakeholders, divided into two, namely the main and secondary groups and the data collected through questionnaire forms, interviews and Focus Group Discussions (FGD) in Cilacap districk.&#x0D; The collected data was analysed using scoring method with various respondents. Stakeholders give a rating or value of 1,2,3,4 on the strengths and opportunities factors, Giving a rating of 4,3,2,1 for the opposite of the level of importance of the weaknesses and threats factors.&#x0D; The strategy formulations used are SWOT analysis using the Strength, Weakness, Opportunity, Threats (SWOT) and Quantitative Strategic Planning Matrix (QSPM) analysis. The matching of the selected strategy is Strength Opportunity (SO) with the largest score: 1.34 and 1.06. The strategic priorities are area and fishing time with a Total Attractive Score (TAS) of 4.2439, increasing fishermen's human resources (4.0715), modernizing and modifying fleets and lay gill nets (3.6098), utilizing potential for export needs (3.317).

Biological and life-history parameters for Labeo rosae Steindachner, 1894 and Oreochromis mossambicus (Peters, 1852) from Flag Boshielo Dam, Olifants River, South Africa

Inland fisheries contribute towards food security for rural communities living close to large aquatic systems. However, sustainable inland fisheries rely on accurate biological information for the target species at the proposed fishery location. In this study, the biological information for Labeo rosae Steindachner, 1894 and Oreochromis mossambicus (Peters, 1852) were determined at Flag Boshielo Dam, Olifants River system, Limpopo province, as part of a larger study to evaluate a small-scale gill net fishery at this impoundment. Nine fish surveys were conducted from February 2016 to April 2017 using mixed sampling gears. Labeo rosae exhibited positive allometric growth (b > 3) while O. mossambicus displayed negative growth (b < 3). For L. rosae, the asymptotic length was 391 mm L ∞, and the length-at-50% sexual maturity 165.8 mm. For O. mossambicus, the asymptotic length was 420 mm L ∞, and the length-at-50% sexual maturity 166.5 mm. Both species population stocks showed signs of exploitation. Total mortality for L. rosae was 0.57 yr−1 with a fishing exploitation of 0.21 yr−1, while total mortality of 0.78 yr−1 and fishing exploitation of 0.50 yr–1 were estimated for O. mossambicus. The biological data collected, apart from the length–weight parameters for O. mossambicus, are suitable for conducting a fisheries assessment for these species at Flag Boshielo Dam.

Guarding net effects on landings and discards in Mediterranean trammel net fishery: Case analysis of Egadi Islands Marine Protected Area (Central Mediterranean Sea, Italy)

Discards remain among the main negative impacts of fishing activities, and their reductions are strengthened by the European Common Fisheries Policy (European Regulation 1380/2013). Trammel net fisheries appear more sustainable compared with other fishing techniques, especially from an ecological viewpoint. Despite this, reports show that trammel net fisheries deliver discard quantities between 10% and 43% of the total catch biomass. To supplement existing information, this current work attempts to address the discard reduction using guarding net in the small-scale fisheries of Egadi Islands MPA (Western Sicily, Central Mediterranean Sea). To assess the reduction of unwanted catches, 48 experimental fishing trials were conducted within a 6-month period. The experimental fishing trial employed a trammel net made up of 20 panels alternated with two different net configurations. The control panels (CN) held a large outer (180 mm) and small inner (31.25 mm) meshes. The test panels (GN) with guarding net constituted a three-mesh-high (50-mm mesh size) net placed between trammel net panels and a lead line. A total of 3,310 individuals belonging to 106 taxa and nine phyla were caught. Crustaceans were the most abundant unwanted catches in the control panels, whereas bioconstructions occurred in the guarding net panels. The discard ratios of CN and GN panels were statistically different (t-value = –2.55; p&amp;lt; 0.05). The analysis of catch per unit effort showed higher catches of CN panels for both commercial and discard fractions (p&amp;lt; 0.05). Moreover, the guarding net panels caught the main discarded species at 20% lower compared with the control. The overall value of the catch at the CN panels (€ 3,366.90) was higher than the total income (€ 2,043.70) generated using the GN panels, which suggests a significant commercial loss of 40% (p&amp;lt; 0.05).

Resource Use among Six Commercial Fish Species from the South-Eastern Gill Net Fisheries, Korea

Dietary habits and inter-specific differences in resource use among six commercial fish species, Chelidonichthys spinosus, Cleisthenes pinetorum, Glyptocephalus stelleri, Hexagrammos otakii, Lophius litulon, and Sebastes schlegelii, collected from the southern coast of the East Sea, Korea, were analyzed using stomach content and stable isotope analyses. Teleosts were the main prey items for C. pinetorum and L. litulon, while both crabs and teleosts contributed to the diets of C. spinosus and S. schlegelii. Glyptocephalus stelleri mainly consumed polycheates and carid shrimps, and H. otakii mostly ingested crabs. The composition of prey items was significantly different in the diets of the six fish species. Further, carbon (δ13C) and nitrogen (δ15N) stable isotope values were significantly different among the six species, indicating different trophic positions. L. litulon, C. pinetorum, and S. schlegelii had narrow niches, whereas C. spinosus, G. stelleri, and H. otakii had relatively wider niches. This study demonstrated differences in patterns of food resource use among the six fish species that were categorized into two patterns of resource use according to their main prey items: diet diversity, trophic niche width, and trophic position. These results could contribute to the understanding of trophic relationships among fish species inhabiting the East Sea, Korea.

High‐frequency pingers do not increase catch loss owing to seals in the Baltic Sea

Abstract The Baltic Proper harbour porpoise population is listed as Critically Endangered by IUCN, and only a few hundred animals remain. One of the most serious threats to this population is bycatch in static net fisheries. To minimize bycatch, ICES has proposed that acoustic deterrent devices, pingers, should be used on static nets within the population’s range. However, there have previously been indications that grey seals learn to associate the pinger sounds with the presence of nets with easily accessible prey, and that pinger use therefore can increase the risk of seal depredation in static net fisheries. In recent years, pingers operating at higher frequencies have been made commercially available, the idea being that harbour porpoises will still be able to hear the sound at 50–120 kHz while this will be above or at the limit of seal hearing. This would mean that such high‐frequency pingers would not induce this so‐called dinner‐bell effect. In this study, data were collected from active commercial static net fisheries in the Baltic Proper, using two types of high‐frequency pingers operating at 50–120 and 70 kHz, respectively. Pingers were attached to nets in accordance with manufacturers’ guidelines, and fishers were asked to estimate the catch loss owing to seals in nets with and without pingers. Data were received from 646 deployments made between May 2019 and September 2020. Four generalized mixed effect models were developed with relevant variables. The results suggest using high‐frequency pingers does not increase seal depredation on static nets. It is concluded that pingers could be used as an interim measure to minimize bycatch of the Critically Endangered Baltic Proper harbour porpoise population.

A socio‐psychological approach for understanding and managing bycatch in small‐scale fisheries

Abstract Fisheries bycatch is the greatest threat to migratory, long‐lived marine animals. Addressing bycatch ultimately requires changing fisher behaviour, yet social and behavioural sciences are rarely applied to bycatch mitigation, with an absence of theory‐informed behaviour change interventions. Moreover, mitigating bycatch is particularly challenging in small‐scale mixed‐species fisheries (SSFs), where perceptions of target and non‐target vary widely, and all catches have economic or subsistence value. Such fisheries are ubiquitous throughout the world's oceans, and bycatch mitigation in these contexts necessitates a people‐centred approach. We seek to address this gap, drawing on well‐established theories from behavioural and social sciences. We first typify bycatch as a spectrum rather than a clearly delineated component of catch, where the position of a species on this spectrum depends on fishers' beliefs regarding the outcomes of bycatch‐relevant behaviour. We then outline an approach to ‘diagnose’ fishers' underlying beliefs about bycatch, using the theory of planned behaviour (TPB): a widely applied and empirically tested theory for predicting and changing behaviour. Finally, we illustrate the approach using an empirical case study, exploring fishers' beliefs regarding bycatch‐relevant behaviour for three endangered elasmobranch species in a small‐scale gill net fishery in Indonesia. Our findings show how the TPB can help to understand fishers' underlying beliefs regarding bycatch, and facilitators/inhibitors of bycatch mitigation, to inform behaviour change interventions. We emphasize the need to understand the human dimensions of bycatch, especially in SSFs, where technical fixes alone will be insufficient to change behaviour. Rather, interdisciplinary approaches are needed to align fishers' needs with conservation objectives. Our bycatch spectrum and the TPB could be widely applied for disentangling drivers of bycatch in other SSFs and designing interventions which support more effective and socially just marine conservation. Read the free Plain Language Summary for this article on the Journal blog.

The dominance of non-indigenous species in the catch composition of small-scale fisheries: A case study from the Kaş–Kekova Special Environmental Protection Area, Türkiye, Eastern Mediterranean

This study aimed to determine the catch composition and compare the catch per unit effort (CPUE) of indigenous and non-indigenous species in longline and trammel net fisheries in the Mediterranean coasts of Türkiye. The data were collected weekly from May 2020 to September 2021 by commercial fishing vessels (n = 62 days for trammel nets, n = 75 days for longlines). The results of the study indicated that more than 90% of the catch composition consisted of non-indigenous species in trammel net fishery and Pterois miles (Bennett, 1828), Siganus rivulatus Forsskål et Niebuhr, 1775, Siganus luridus (Rüppell, 1829), and Scarus ghobban Forsskål, 1775 were the most commonly caught species. Although indigenous species were more common in longlines compared with trammel nets, non-indigenous species Lagocephalus sceleratus (Gmelin, 1789) and Lagocephalus suezensis Clark et Gohar, 1953 were represented by relatively high catch ratios. The results also revealed that the CPUE of non-indigenous species exhibited seasonal differences. Although some non-indigenous species caught within this study have a market value, some other highly invasive species do not. Therefore, it is critically important to develop effective management tools to control bio-invasion. This study provides the first comprehensive research by utilizing basic data with relatively long-term surveys in the small-scale fishery on the Mediterranean coasts of Türkiye. The outcomes of this study can provide guidance to decision-makers.

Study of Types and Production of Trap Net Fishery Fish based on Moon Phase in the Waters of Segeri District, Pangkep Regency, South Sulawesi Indonesian

The research was carried out in October-November 2020 in the waters of the Pangkep Regency. The data collected consisted of primary and secondary data, using direct observation in the field. Tidal observations were carried out in every moon phase for 2 x 24 hours. I collected data on the type and number of catches in each month’s phase. Tidal analysis using the criminal method and descriptive analysis of the types and quantities of trap net fish production (kg) and (Rp). The full moon phase is the highest tide at 185 cm and the lowest at 42 cm. The average sea level (mean sea level) is 113.5 cm. Types of trap net catch based on the moon phase in the waters of Sergei District, Pangkep Regency, identified 13 types of catches. The highest amount of fish production was obtained by the full moon phase of 100 kg, followed by the 80 kg dead moon phase, 95 kg early quarter moon, and 65 kg final quarter moon phase.

An investigation of acoustic deterrent devices to reduce cetacean bycatch in an inshore set net fishery

In Europe, problems with the use of pingers on larger fishing vessels have raised the question as to whether pingers would be practical on smaller vessels, which are a large proportion of the European static net fishing fleet. In this study, four netting vessels less than 10m long used AQUAmark pingers on part of their nets off the southwest coast of Britain over a 12 month period. Boat skippers recorded ease of use. Acoustic click detectors were deployed on test and control nets to assess the response of cetaceans to the pingers. No significant practical problems, apart from premature failure of pingers, were encountered. During the study, only one harbour porpoise was bycaught, in an unpingered net. In 650 days of acoustic data from pingered and non-pingered nets, matched by location, date and boat, there was a highly significant reduction in the number of porpoise clicks recorded at nets with pingers to 48% of the number predicted from the number recorded at control nets (range 35–51%). To assess habituation, single, modified pingers that were active for alternate seven hour periods were moored below a click detector at two sites, one of which has strong tides and high levels of associated ambient noise. This study showed a stronger pinger effect at the quiet site and a much reduced effect at the noisy site. There was evidence of a period of exclusion of porpoises following pinger use that could exceed seven hours, and no evidence of habituation. Results suggest that pingers are practical on small vessels, that they reduce harbour porpoise activity around nets and are therefore likely to reduce bycatch. Easier means of detecting pinger failure are needed. Pingers should be considered as a bycatch mitigation method in small vessel fisheries using bottom set nets.