The Experts below are selected from a list of 846 Experts worldwide ranked by ideXlab platform

Andrea D. Marshall - One of the best experts on this subject based on the ideXlab platform.

Joshua D Stewart - One of the best experts on this subject based on the ideXlab platform.

  • High bycatch rates of manta and devil rays in the “small-scale” artisanal fisheries of Sri Lanka
    'PeerJ', 2021
    Co-Authors: Daniel Fernando, Joshua D Stewart
    Abstract:

    Background Expanding fisheries in developing nations like Sri Lanka have a significant impact on threatened marine species such as elasmobranchs. Manta and devil (mobulid) rays have some of the most conservative life history strategies of any elasmobranch, and even low to moderate levels of bycatch from gillnet fisheries may lead to significant population declines. A lack of information on life history, demographics, population trends, and fisheries impacts hinders effective management measures for these species. Method We report on mobulid fishery landings over nine years between 2011 and 2020 across 38 landing sites in Sri Lanka. We collected data on catch numbers, body sizes, sex, and maturity status for five mobulid species. We used a Bayesian state-space model to estimate monthly country-wide catch rates and total annual landings of mobulid rays. We used catch curve analyses to estimate total mortality for Mobula Mobular, and evaluated trends in recorded body sizes across the study period for M. Mobular, M. birostris, M. tarapacana and M. thurstoni. Results We find that catch rates have declined an order of magnitude for all species across the study period, and that total annual captures of mobulid rays by the Sri Lankan artisanal fishing fleet exceed the estimated annual captures of mobulids in all global, industrial purse seine fisheries combined. Catch curve analyses suggest that M. Mobular is being fished at rates far above the species’ intrinsic population growth rate, and the average sizes of all mobulids in the fishery except for M. birostris are declining. Collectively, these findings suggest overfishing of mobulid ray populations in the northern Indian Ocean by Sri Lankan artisanal fisheries. We recommend strengthening the management of these species through improved implementation of CITES, CMS, and regional fisheries management actions. In addition, we report on the demographic characteristics of mobulids landed in Sri Lanka and provide the first record of M. eregoodoo in the country

  • Environmental characteristics associated with the presence of the Spinetail devil ray (Mobula Mobular) in the eastern tropical Pacific.
    'Public Library of Science (PLoS)', 2019
    Co-Authors: Nerea Lezama-ochoa, Martin A Hall, Maria Grazia Pennino, Joshua D Stewart, Jon López, Hilario Murua
    Abstract:

    In the eastern Pacific Ocean, the tropical tuna purse-seine fishery incidentally captures high numbers of five mobulid bycatch species; all of which are classified as mortalities by the Inter-American Tropical Tuna Commission due to uncertainties in post-release mortality rates. To date, the factors (operational or environmental) leading to the capture of these species by the fishery have not been well studied. Here, we developed Generalized Additive Models for fisheries observer data to analyze the relationships between the presence/absence of Mobula Mobular bycatch and oceanographic conditions, the spatial and temporal variability in fishing location, and the set type (associated with dolphins, free-swimming tuna schools or floating objects). Our results suggest that chlorophyll concentration and sea surface height are the most important variables to describe the presence of M. Mobular in conjunction with geographic location (latitude and longitude) and set type. Presence of the species was predicted in waters with chlorophyll concentrations between 0.5-1 mg·m-3 and with sea surface height values close to 0; which indicates direct relationships with productive upwelling systems. Seasonally, M. Mobular was observed more frequently during December-January and August-September. We also found the highest probability of presence observed in School sets, followed by Dolphin sets. Three areas were observed as important hotspots: the area close to the coastal upwelling of northern Peru, the area west to Islands Colon Archipelago (Galapagos) and the area close to the Costa Rica Dome. This information is crucial to identify the mobulids habitat and hotspots that could be managed and protected under dynamic spatial management measures to reduce the mortality of mobulid rays in the eastern Pacific purse-seine fishery and, hence, ensure the sustainability of the populations of these iconic species

  • characterization of the trade in manta and devil ray gill plates in china and south east asia through trader surveys
    Aquatic Conservation-marine and Freshwater Ecosystems, 2017
    Co-Authors: Mary P Omalley, Kathy A Townsend, Paul Hilton, Shawn Heinrichs, Joshua D Stewart
    Abstract:

    Dried gill plates from manta and devil rays, some of the world's most biologically vulnerable fishes, have become a valued commodity in Asian dried-seafood and traditional Chinese medicine markets. This trade is a primary driver of fisheries, which have led to declines in many mobulid populations. With no reliable trade statistics and scarce data on mobulid fisheries, this study estimates the number and species of mobulids required to supply this trade, and investigates the consumers and suppliers involved and drivers of demand. Following preliminary market research, 525 trader surveys were conducted in Hong Kong, Singapore, Macau, Taiwan, and southern China. Guangzhou, China was identified as the centre of the trade accounting for 99% of total estimated market volume of 60.5 tons of dried gill plates in 2011, increasing to 120.5 tons by 2013. The estimated number of mobulids converted from tons of gill plates more than doubled over the period to 130 000, comprising 96% devil rays, Mobula japanica, Mobula thurstoni, and Mobula tarapacana, and 4% Manta spp. By 2015 the Guangzhou market had declined sharply, reportedly due to conservation campaigns and government policies. However Hong Kong's gill plate sales increased dramatically between 2011 and 2015. China, Indonesia, Vietnam, Sri Lanka, and India were reported most frequently as gill plate sources. Vendors recommend gill plates (trade name pengyusai) for ailments ranging from acne to cancer and as a general health tonic. While pengyusai is a new addition to traditional Chinese medicine literature and is rarely prescribed by traditional medicine practitioners, it is readily available over the counter and aggressively marketed by vendors. Working in concert with consumer demand reduction efforts, increased measures to restrict mobulid fisheries and trade are recommended to prevent further population declines of these highly vulnerable species. Copyright © 2016 John Wiley & Sons, Ltd.

Neil R. Loneragan - One of the best experts on this subject based on the ideXlab platform.

  • Image_10_Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia.jpg
    2019
    Co-Authors: Elitza S. Germanov, Simon J. Pierce, Lars Bejder, Delphine B. H. Chabanne, Dharmadi Dharmadi, Gede I. Hendrawan, Andrea D. Marshall, Mike Van Keulen, Neil R. Loneragan
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

  • Image_6_Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia.jpg
    2019
    Co-Authors: Elitza S. Germanov, Simon J. Pierce, Lars Bejder, Delphine B. H. Chabanne, Dharmadi Dharmadi, Gede I. Hendrawan, Andrea D. Marshall, Mike Van Keulen, Neil R. Loneragan
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

  • Table_1_Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia.docx
    2019
    Co-Authors: Elitza S. Germanov, Simon J. Pierce, Lars Bejder, Delphine B. H. Chabanne, Dharmadi Dharmadi, Gede I. Hendrawan, Andrea D. Marshall, Mike Van Keulen, Neil R. Loneragan
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

Lydie I. E. Couturier - One of the best experts on this subject based on the ideXlab platform.

Dharmadi Dharmadi - One of the best experts on this subject based on the ideXlab platform.

  • Image_10_Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia.jpg
    2019
    Co-Authors: Elitza S. Germanov, Simon J. Pierce, Lars Bejder, Delphine B. H. Chabanne, Dharmadi Dharmadi, Gede I. Hendrawan, Andrea D. Marshall, Mike Van Keulen, Neil R. Loneragan
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

  • Image_6_Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia.jpg
    2019
    Co-Authors: Elitza S. Germanov, Simon J. Pierce, Lars Bejder, Delphine B. H. Chabanne, Dharmadi Dharmadi, Gede I. Hendrawan, Andrea D. Marshall, Mike Van Keulen, Neil R. Loneragan
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

  • Table_1_Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia.docx
    2019
    Co-Authors: Elitza S. Germanov, Simon J. Pierce, Lars Bejder, Delphine B. H. Chabanne, Dharmadi Dharmadi, Gede I. Hendrawan, Andrea D. Marshall, Mike Van Keulen, Neil R. Loneragan
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

  • Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia
    'Frontiers Media SA', 2019
    Co-Authors: Germanov, Elitza S, Dharmadi Dharmadi, Bejder Lars, Chabanne, Delphine B H, Hendrawan I Gede, Marshall, Andrea D, Pierce, Simon J, Van Keulen Mike, Loneragan, Neil R
    Abstract:

    Manta rays (Mobula spp.) are highly valued in nature-based tourism globally. In Indonesia, although manta rays are protected, critical information is lacking on their habitat use, population dynamics and movements. We investigate the population structure and residency patterns of reef manta rays (Mobula alfredi) in the Nusa Penida Marine Protected Area (MPA). From photo-identification data logged by citizen scientists and trained observers (mantamatcher.org), we identified 624 reef manta rays from 5,913 sightings (January 2012–April 2018) based on their unique ventral coloration patterns. Year-round records were collected from two shallow (

  • PERIKANANDANASPEKBIOLOGI IKANPARI LAMPENGAN, Mobula japanica DI PERAIRANSELATAN JAWA
    'Agency for Marine and Fisheries Research and Development', 2017
    Co-Authors: Dharmadi Dharmadi, Sunarno, Mas Tri Djoko, Edrus, Isa Nagib
    Abstract:

    Ikan pari merupakan salah satu jenis ikan yang banyak didaratkan berasal dari Selatan Jawa. Salah satu jenis ikanpari yang belum banyak dilakukan penelitian adalah ikan pari lampengan (Mobula japanica). Tujuan penelitian ini adalah untuk mengetahui tentang perikanan dan aspek biologi jenis ikan tersebut di perairan Selatan Jawa sebagai informasi dasar bagi penentuan kebijakan pengelolaan perikanan Elasmobranchii. Penelitian menggunakan metode survei yang berlangsung dari Januari hingga Desember 2010 di Pelabuhan Perikanan Samudera Cilacap-Jawa Tengah. Sejumlah 165 ikan pari yang tertangkap oleh jaring insang diamati tingkat kematangan seksual, tingkat kematangan gonad, jenis kelamin dan ukuran lebar cawannya.Wawancara dilakukan terhadap para nelayan dan nahkoda kapal yang menangkap ikan pari lampengen tersebut secara langsung dan atau oleh enumerator. Hasil penelitian menunjukkan bahwa tangkapan per satuan usaha (CPUE) ikan pari lampengan bervariasi, yakni tertinggi pada bulan Juli (22,6 kg/ hari) dan terendah pada bulan Oktober (6,6 kg/hari). Frekuensi lebar tubuh ikan pari lempengen terendah terdapat pada ukuran antara 100-140 cmdenganmodus 120 cmyang termasuk kelompokmuda, sedangkan ukuran antara 150- 200 cm dengan modus 170 cm, termasuk kelompok dewasa. Frekuensi lebar tubuh tertinggi terdapat pada ukuran antara 200-260 cmdenganmodus 230 cm. Ikan pari lempengen sedikitnya terdiri atas 3 kelompok umur dengan modus sebaran lebar tubuh masing-masing 120, 170, dan 230 cm. Hubungan lebar tubuh (y) dan panjang klasper (x)mengikuti persamaan y=0,3784e0,0131x (r2=0,85), semakin bertambah lebar tubuh semakin bertambah panjang klaspernya.Perbandingan kelamin jantan dan betina adalah tidak seimbang (1,5:1). Sebagian besar kelompok umur ikan pari lampengan yang tertangkap tergolong usia muda, yang belummencapai pertumbuhan optimum(growth over fishing). Stingray is one of the species of fish that many landed came from the South of Java. One of the species that have not many research is JapaneseDevilray (Mobula japanica). The purpose of this study was to determine fisheries and biological aspects of Japanese Devilray, Mobula japanica in Indian Ocean as basic information for managing the elasmobranches fisheries. This study was conducted from January to December 2010 in the Ocean Fishing Port of Cilacap, Central Java. A total number of 165 individu of M. japanica caught by seine net and tuna longline were observed during the sampling periods. Body wide, sex, and gonadmaturation of those fishes were analyzed. Interviewswere also done to the fisherman and fishing master. The results showed that the body width of stingrays, M. japanica had the lowest frequency between 100-140 cm with mode of 120 cm,and grouped as young fish.Other groups has body width between 150-200 cm with mode 170 cm, and grouped as adult fishes. While the frequency of the highest body width was between 200-260 cm and 230 cmmode. At least, there were 3 cohorts ofM. japanica found in this study with the body width mode of 120, 170 and 230 cm. Exponential relationship between body width (y) and claspers’ length (x) was observed forM. japanica, that expressed by equation: y=0.3784e 0.0131x (r2=0.85), that mean the more width fish body, the more increase claspers’ length. Unbalance sex ratio of 1.5:1 was observed for this fish. CPUE for M. japanica were varied between 6,6 kg/day during October and 22,6 kg/day 0n July. Most of fish caught were young fishes under their maturity stages that indicated a tendency of growth over fishing