Preliminary results of a study into the incidental mortality of sharks in Gill-nets in two Tasmanian Shark Nursery Areas

Since the early 1960s, certain sheltered bays and estuaries around Tasmania have been designated shark nursery areas, where the taking of either the school shark (Galeorhinus galeus) or the gummy shark (Mustelus antarcticus) has been prohibited. Recent assessments of Australian stocks of school and gummy sharks indicate that they are close to collapse, and the management of the fishery has come under review. With respect to shark nursery areas, concern has focused on the potential rate of incidental mortality of sharks caused by recreational gill-net fishing and poaching. In 1990, a study was begun in Frederick Henry Bay and Norfolk Bay, the largest proclaimed shark nursery areas in Tasmania, to estimate recreational net-fishing effort and incidental captures of sharks. School sharks were caught in waters deeper than 5 m; gummy sharks and dogfish were caught at all depths. The diversity and relative abundance of shark species increased with depth, whereas the diversity of teleosts decreased with depth. Most captured school and gummy sharks were between 1+ and 3+ years of age. Preliminary estimates of potential incidental mortality demonstrate that gill-netting in depths greater than 5 m may be a significant source of mortality for both species.

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Shark fisheries in Argentina

Marine and Freshwater Research ◽

10.1071/mf97136 ◽

1998 ◽

Vol 49 (7) ◽

pp. 601 ◽

Cited By ~ 30

Author(s):

Gustavo E. Chiaramonte

Keyword(s):

Fishing Effort ◽

Population Trends ◽

The South ◽

Gill Nets ◽

Argentine Sea ◽

Commercial Importance ◽

South West ◽

Gill Net ◽

Galeorhinus Galeus ◽

Mustelus Schmitti

In the Argentine Sea there are about 35 species of sharks. Three species are subjected to directed fishing: the smoothhound Mustelus schmitti, the school shark Galeorhinus galeus and the copper shark Carcharhinus brachyurus. Other species of elasmobranchs with commercial importance are the angel shark Squatina spp. and several species of skates and rays. The rise in chondrichthyan declared landings registered from 1988 to 1996 is due to the increase in landings of smoothhound and rays. The most important directed shark fishery in the South-West Atlantic is the Necochea gill-net fishery for school shark, which is carried out by the coastal fleet; details are given of the ships and the gill-nets used in this area. The length frequencies of the catches by gill-nets are presented for the school shark; fishing effort (length (km) of net in the water per ship per day) and CPUE (number of sharks per fishing effort) were found not to be good indicators of population trends in the school shark fishery. Resumen. En el Mar Argentino se han registrado 35 especies de tiburones. Tres de estas especies están sometidas a una pesca dirigida; el gatuzo, Mustelus schmitti, el cazón, tiburón vitamínico o trompa de cristal, Galeorhinus galeus y la bacota, Carcharhinus brachyurus. Otras especies de elasmobranquios de importancia comercial son el pez ángel Squatina spp. y algunas especies de rayas. El incremento en los desembarcos de condríctios declarados a las autoridades pesqueras entre 1988 y 1996 es debido principalmente al incremento del desembarco de gatuzo y rayas. La pesquería dirigida a tiburón más importante en el Atlántico Sudoccidental es la pesquería costera de enmalle de Necochea para el cazón. Se describen el largo de las embarcaciones y las redes utilizadas en el área (la medida de malla, el calado y la operación del arte de pesca). Se presenta la frecuencia del largo total de las capturas de cazón en redes de enmalle. Se halló para la pesquería del cazón que el esfuerzo pesquero (estimado como km de red en el agua por embarcación por día) y la CPUE (estimada como tiburones/esfuerzo de pesca) no son buenos indicadores de la tendencia en la abundancia poblacional.

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Factors affecting relative abundance of low-mobility fishing resources: spiny lobster in the Galapagos Marine Reserve

PeerJ ◽

10.7717/peerj.7278 ◽

2019 ◽

Vol 7 ◽

pp. e7278 ◽

Cited By ~ 1

Author(s):

Juan Carlos Murillo-Posada ◽

Silvia Salas ◽

Iván Velázquez-Abunader

Keyword(s):

Monitoring System ◽

Relative Abundance ◽

Spatial Scales ◽

Marine Reserve ◽

Spiny Lobster ◽

Fishing Effort ◽

Additive Models ◽

Catch Per Unit Effort ◽

Monthly Basis ◽

Galapagos Marine Reserve

Management of low-mobility or benthic fisheries is a difficult task because variation in the spatial distribution and population dynamics of the resources make the monitoring and assessment of these fisheries challenging. We assumed that environmental, spatial, and temporal factors can contribute to the variability of the relative abundance of such species; we used Generalized Additive Models for Location Scale and Shape (GAMLSS) to test this hypothesis using as a case study the lobster fishery (targeting two species) in the Galapagos Marine Reserve, Ecuador. We gathered data on each of the two species of lobster on a monthly basis over seven years, including: (a) onboard observers’ records of catch data, fishing effort, and ground location by trip, and (b) data from interviews undertaken with fishers at their arrival to port, recording the same type of information as obtained from onboard observers. We use this information to analyze the effect of the measured variables and to standardize the Catch per Unit Effort (CPUE) in each case, using the GAMLSS. For both species, the temperature, region, fishing schedule, month, distance, and the monitoring system were significant variables of the selected models associated with the variability of the catch rate. ForPanulirus penicillatus, CPUE was higher at night than during the day, and forPanulirus gracilisit was higher during the day. Increased temperature resulted in a decrease of CPUE values. It was evident that temporal, spatial scales and monitoring system can influence the variability of this indicator. We contend that the identification of drivers of change of relative abundance in low-mobility species can help to support the development of monitoring and assessment programs for this type of fisheries.

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Population genetics of the school shark (Galeorhinus galeus) in New Zealand, Australian and Chilean waters

10.26686/wgtn.17005726.v1 ◽

2021 ◽

Author(s):

◽

Sebastián Ignacio Hernández Muñoz

Keyword(s):

Genetic Diversity ◽

New Zealand ◽

Dna Markers ◽

Microsatellite Dna ◽

Multiple Paternity ◽

Shark Species ◽

Microsatellite Dna Markers ◽

Minimum Number ◽

Galeorhinus Galeus ◽

Shark Fisheries

The school shark (Galeorhinus galeus) is a coastal bentho-pelagic species that is highly migratory and has a widespread distribution in temperate waters. This species matures late, has a relatively low fecundity and is slow growing, which makes it vulnerable to overfishing. They are commercially fished throughout their distribution, and some global stocks have been under pressure because of poor management. In Australia, longline and gillnet fisheries targeted pregnant females and juveniles around Victorian and Tasmanian nursery grounds, resulting in loss of historical inshore nursery habitat. School shark tagging programmes have reported migration between Australian and New Zealand stocks, but preliminary genetic studies have suggested that there are slight genetic differences between the stocks. Currently, the Australian and New Zealand school shark fisheries are assessed and managed as separate stocks. However, the question of whether this species is comprised of a single population or multiple sub-populations in the South Pacific remains unresolved. Given the commercial importance of the school shark fisheries and the concern about stock levels on the regional and trans-Tasman scales, knowledge of stock structure is essential for effective management. The aim of this thesis research was to determine the levels of genetic diversity and population structure of G. galeus in New Zealand and Australia, and compare these to a population in Chile, using mitochondrial DNA (mtDNA) sequencing and microsatellite DNA markers. The DNA sequence of an 893 base pair region of the mtDNA control region (CR) was determined using 475 school shark samples and nine microsatellite DNA loci were genotyped in 239 individuals. Analyses of the data revealed strong evidence of genetic differentiation between G. galeus populations in Australasia and Chile, suggesting restricted gene flow among populations in the western and eastern areas of the Pacific Ocean. The FST values ranged from 0.188 to 0.300 for CR mtDNA, and 0.195 to 0.247 for microsatellite DNA in G. galeus. However, there was no evidence of stock differentiation among New Zealand/Australian sample sites for either mtDNA or microsatellite DNA data. These results support the model of a single panmictic stock across the Tasman Sea. The similarity of the results obtained from the maternally inherited mtDNA and biparental inherited microsatellite loci did not support the suggestion of sex-biased dispersal of G. galeus in the New Zealand/Australia region and it was concluded that females and males had similar patterns of dispersal. Sharks can be either monogamous or polygamous, which is important when considering stock assessments and harvesting models. Multiple paternity has been reported in several shark species, however, the number of sires per litter varies considerably among species. An investigation of multiple paternity (MP) was conducted in G. galeus by assessing the levels of relatedness within progeny arrays using six polymorphic microsatellite DNA markers. Five “families” (mother and litters) were sampled from the North Island of New Zealand and a parentage analysis was conducted. The minimum number of males contributing to each progeny array was estimated by identifying the putative paternal alleles by allele counting and reconstructing multilocus genotypes method. The analysis showed the occurrence of genetic polyandry in G. galeus; two of five litters showing multiple sires involved in the progeny arrays (40%). The minimum number of sires per litter ranged from one to four. Although MP was only detected in two litters, this finding is consistent with the known reproductive characteristics of G. galeus. It can potentially store sperm for long periods of time and has a specific mating season when males and females typically mix on the edge of the continental shelf. Detecting MP within a litter has highlighted the importance of the post-copulatory selective processes in the G. galeus mating system, and this has implications for the management and conservation of genetic diversity.

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Shark Nursery Grounds of the Gulf of Mexico and the East Coast Waters of the United States

Shark Nursery Grounds of the Gulf of Mexico and the East Coast Waters of the United States ◽

10.47886/9781888569810.ch10 ◽

2007 ◽

Keyword(s):

United States ◽

Gulf Of Mexico ◽

East Coast ◽

Gulf Coast ◽

Atlantic Coast ◽

The United States ◽

Shark Species ◽

Carcharhinus Plumbeus ◽

Nursery Areas ◽

Pesticide Metabolites

Abstract.—Because of their tendency to accumulate in estuaries and coastal regions, organochlorine (OC) contaminants such as pesticides and polychlorinated biphenyls (PCBs) represent potential threats to the quality of essential fish habitat for many shark species. These compounds pose special risks to immature sharks in particular because of their ability to impair growth and sexual maturation in juvenile fish at environmentally relevant levels of exposure. In order to assess the extent of these risks in shark populations on the East Coast of the United States, the present study examined concentrations of 30 OC pesticides/pesticide metabolites and total PCBs in juvenile sandbar Carcharhinus plumbeus and blacktip C. limbatus sharks from seven major nursery areas in the western Atlantic Ocean and eastern Gulf of Mexico. Quantifiable levels of PCBs and 13 OC pesticides/ pesticide metabolites were detected via gas chromatography and mass spectrometry in liver of 25 young-of-the-year blacktip sharks from the southeastern U.S. Atlantic coast and three regions on Florida’s gulf coast: Cedar Key, Tampa Bay, and Charlotte Harbor. Similarly, quantifiable levels of PCBs and 14 OC pesticides/metabolites were detected in 23 juvenile C. plumbeus from three sites on the northeastern U.S. coast: middle Delaware Bay, lower Chesapeake Bay, and Virginia’s eastern shore. Liver OC concentrations in Atlantic sandbar and blacktip sharks were higher than expected and, in some cases, comparable with elevated levels observed in deep-sea and pelagic sharks. Although significantly lower than those observed in Atlantic sharks, pesticide and PCB levels in Florida blacktip sharks were similar to, if not greater than, OC concentrations reported in adults of other coastal shark species. Based on these data, OC contamination appears to pose significant threats to habitat quality in sandbar and blacktip shark nursery areas on the U.S. Atlantic coast.

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Incidental capture of elasmobranchs in the bottom-set gill-net fishery off the south coast of Ireland

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400090081 ◽

1994 ◽

Vol 74 (4) ◽

pp. 837-847 ◽

Cited By ~ 11

Author(s):

S.D. Berrow

Keyword(s):

Fishing Effort ◽

South Coast ◽

Fishing Gear ◽

The South ◽

Blue Shark ◽

Incidental Capture ◽

Gill Net ◽

Total Capture ◽

Catch Rates ◽

Basking Shark

The incidental capture of sharks in the bottom-set gill-net fishery off the south coast of Ireland was quantified by placing observers on commercial gill-netters for the duration of a fishing trip. Forty fishing trips were sampled resulting in 1,167 km and 19,760 km h of observed fishing effort. Sixty individual sharks of seven species were reported entangled in the fishing gear. Tope, porbeagle and six-gilled sharks were the most frequently caught species, with black-mouthed dogfish, blue shark, basking shark and starry smooth hound also recorded. Total fishing effort along the south coast was calculated and total capture extrapolated from observed catch rates. An estimated 6,000 sharks were caught in this fishery during the study period.

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Fisheries management in the face of uncertainty: Designing time-area closures that are effective under multiple spatial patterns of fishing effort displacement in an estuarine gill net fishery

PLoS ONE ◽

10.1371/journal.pone.0211103 ◽

2019 ◽

Vol 14 (1) ◽

pp. e0211103 ◽

Cited By ~ 5

Author(s):

Liza A. Hoos ◽

Jeffrey A. Buckel ◽

Jacob B. Boyd ◽

Michael S. Loeffler ◽

Laura M. Lee

Keyword(s):

Spatial Patterns ◽

Fisheries Management ◽

Fishing Effort ◽

Gill Net ◽

The Face

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KAPASITAS PENANGKAPAN IKAN PELAGIS KECIL DI PERAIRAN PANTAI BARAT SULAWESI SELATAN (FISHING CAPACITY OF SMALL PELAGIC FISH IN OF WEST COAST OF SOUTH SULAWESI)

Fish Scientiae ◽

10.20527/fs.v1i2.1184 ◽

2016 ◽

Vol 1 (2) ◽

pp. 117 ◽

Cited By ~ 2

Author(s):

Alfa Nelwan

Keyword(s):

West Coast ◽

Fishing Effort ◽

Pelagic Fish ◽

Production Data ◽

Fish Production ◽

Beach Seine ◽

Small Pelagic Fish ◽

South Sulawesi ◽

Gill Net ◽

Development Analysis

Kapasitas penangkapan adalah ukuran kemampuan yang dikerahkan oleh berbagai jenis unit penangkapan ikan yang tergabung sebagai suatu armada penangkapan ikan untuk memperoleh hasil tangkapan. Penelitian ini menganalisis trend dan kapasitas penangkapan ikan pelagis kecil di perairan pantai barat Sulawesi Selatan. Delapan jenis alat penangkap yang signifikan di Selat Makassar, perairan barat Provinsi Sulawesi Selatan adalah payang, pukat pantai, pukat cincin, jaring insang hanyut, jaring lingkar, jaring insang tetap, bagan perahu dan bagan tancap. Produksi dari 8 unit penangkapan berdasarkan 6 jenis ikan pelagis kecil, yaitu (1) kembung (Rastrelliger sp), (2) layang (Decapterus sp), (3) lemuru (Sardinella longiceps), (4) selar (Selaroides spp), (5) tembang (Sardinella fimbriata), (6) teri (Stolephorus spp). Total upaya penangkapan ikan tahunan dari kedelapan jenis unit penangkapan ikan tersebut dihitung untuk kurun waktu selama 20 tahun (1987-2006) dengan menerapkan standardisasi berdasarkan kemampuan setiap jenis unit penangkapan ikan. Analisis dilakukan untuk mengidentifikasi trend CPUE dan kapasitas penangkapan ikan pelagis kecil menggunakan metode Peak to Peak Analysis di tiga zona perairan pantai, yaitu perairan laut dangkal (zona A), perairan bentuk teluk (zona B) dan perairan laut dalam (zona C), Tren CPUE di ketiga zona menunjukkan cenderung menurun dalam kurun waktu 30 tahun, dimana tren menurun CPUE di zona C menunjukkan lebih besar dibandingkan zona lainnya. Kapasitas penangkapan di zona A, perlu mereduksi jumlah unit penangkapan sebesar 6%, sedangkan di zona B sebesar 5% dan zona C sebesar 11% untuk mencapai produksi optimal.Fishing capacity can be regarded as a total mobilized capability made by fishing fleet to produce catch. This research analyze trend and fishing capacities of small pelagic fish in off west coast of South Sulawesi. There are 8 significant fishing unit operated in off west coast of South Sulawesi ; these are payang, beach seine, purse seine, drift gill net, encircling gillnet, fixed gill net, boat liftnet, fixed liftnet. The fish production data cover 6 types of fish, i.e. Indian mackerel, anchovy, sardines, scads, and trevally caught by 8 types fishing unit. Annual fishing effort and CPUE over a period of 30 years (1977-2006) were calculated after a standardization considering variability in capture capability and fisheries development. Analysis was conducted for identifyng CPUE trend and fishing capacities of small pelagic fish using Peak to Peak Analysis. The study area was divided into three regions, i.e, around Spermonde Island (zone A), off Polman and Pinrang district (zone B) and off Majene dan Mamuju district (zone C). CPUE trend in three water zone showed to decrease for 30 year of period, where decreasing CPUE trend at zone C was higher than other zones. Fishing capacities in zone A need to be reduced of fishing effort for 6%, whereas in zone B was 5% and zone C was 11%.

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Linking Fishing Behavior and Ecosystem Dynamics Using Social and Ecological Network Models

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.662412 ◽

2021 ◽

Vol 9 ◽

Author(s):

Joseph J. Luczkovich ◽

Jeffrey C. Johnson ◽

Rebecca A. Deehr ◽

Kevin J. Hart ◽

Lisa Clough ◽

...

Keyword(s):

Fishery Management ◽

Fishing Effort ◽

Ecosystem Dynamics ◽

Ecological System ◽

Regulatory Change ◽

Estuarine Ecosystem ◽

Gill Net ◽

Affiliation Network ◽

Multiple Species ◽

Fishing Behavior

One goal of ecosystem-based management is studying an ecosystem and its people, the socio-ecological system, in a qualitative and quantitative modeling approach that can provide management agencies with possible outcomes of their actions using scenario forecasting. Ecosystem-based fisheries management strives to use the socio-ecological system approach, including direct and indirect impacts on multiple species including the behavioral responses of fishers after a regulatory change (a gillnet ban). Here, we link fisher behavioral networks with a mass-balanced food-web ECOPATH network model of an estuarine ecosystem and its commercial fisheries for an analysis of fishing impacts after a gillnet ban on multiple species using ECOSIM. We modeled fisher behavioral networks using reported catches of species from individual fishers along with the gear fished to create nodes in a gear/species affiliation network. Individual fishers with common gear/species use are indicative of common fishing behavior. When such fishers have high network centrality and are engaged in multiple gear/species fisheries, they can transition to other gear/species fisheries along “switching pathways” when facing a regulatory change. We used an index of joint gear participation to identify likely gear switching pathways, and we predicted changes in fishing effort after a gill net ban. We simulated the gill net ban in ECOSIM under two scenarios of fishing effort: Scenario 1, gill net fishing effort of 0%; Scenario 2, gill net fishing effort of 0% with increased effort in the alternative gear fisheries using the predicted switching pathways for the affiliation network. Scenario 1 predicted an increase in flounder (Paralichthys spp.) biomass over a decade. Under Scenario 2, fishers targeting flounders were predicted to switch from gill nets to pound nets. Scenario 2 predicted a 7% decline in flounder biomass over ten years, rather than an increase in flounders. The gillnet ban with increased effort due to switching is predicted to have the opposite effect on the conservation goal, which was to increase flounder stocks. Fishery management that incorporates a socio-ecological approach modeling both fisher behaviors and multi-species ecosystem responses can reveal single-species responses that are in the opposite direction of the anticipated management goals.

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Surveying Stocks of Scallops (Pecten Maximus) and Queens (Chlamys Opercularis) with Underwater Television

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400024243 ◽

1980 ◽

Vol 60 (1) ◽

pp. 181-191 ◽

Cited By ~ 17

Author(s):

A. Franklin ◽

G. D. Pickett ◽

N. A. Holme ◽

R. L. Barrett

Keyword(s):

Fishing Effort ◽

Pecten Maximus ◽

Preliminary Results ◽

System A ◽

Considerable Research ◽

Underwater Television ◽

The Impact ◽

Still Cameras

In England the fisheries for both scallops (Pecten maximus) and queens (Chlamys opercularis) expanded rapidly in the 1970s. Considerable research has been undertaken to develop an effective method of surveying stocks of these species in order to assess the impact of this greatly increased fishing effort on commercial populations. Visual photographic surveys seemed likely to provide the best means of assessing populations (Pickett & Franklin, 1975) and this paper outlines the preliminary results obtained from such a system - a towed sledge carrying both television and still cameras, developed at the Plymouth Laboratory.

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