Contrasting Habitat Use and Population Dynamics of Reef Manta Rays Within the Nusa Penida Marine Protected Area, Indonesia

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 (<20 m) reefs – Manta Bay (MB; n = 3,029 sightings) and Manta Point (MP; n = 3,058) – that are used frequently by tourism operators. Maximum likelihood techniques and a Markov movement analysis were used to model residency patterns and movement between these sites within the MPA. Manta rays at MB were predominantly male (64%, n = 261 individuals), with immature males (14%, n = 59) being sighted most frequently (39%, n = 1,170). In contrast, few immature individuals were sighted at MP (6%, n = 28), and they were sighted on few occasions (2%, n = 45), while mature female manta rays comprised 26% (n = 127) of the MP community and were the most frequently sighted (48%, n = 1,413). Lagged identification rates indicated high site fidelity at each location. However, 44% (n = 278) of individuals moved between the two sites and cumulative discovery curves showed a continued recruitment of individuals over the 6 years of the study. In addition, the behaviors displayed by the manta rays differed markedly between the two sites: MB appears to be a foraging ground, especially for juveniles, and potentially a nursery, while MP is used mainly for cleaning and courtship, indicating a social and reproductive site. Reproductive behavior coincided with the peak annual sightings in May. To prevent disturbance to this threatened species by tourism, regulations for the number of boats and interactions, especially during key reproductive times should be considered. Further, strict fishing regulation in the area is recommended as fishing gear entanglement was identified as a threat to this population

KONSEP HAK PENGELOLAAN PERIKANAN SEBAGAI ALAT PENGELOLAAN PERIKANAN BERKELANJUTAN DI INDONESIA

Pengelolaan perikanan di Indonesia saat ini belum sepenuhnya mampu mengatasi motivasi perlombaan menangkap ikan. Kondisi yang dikenal sebagai open access ini, perlu segera diatasi untuk mencegah berlanjutnya tangkap lebih. Artikel ini bertujuan untuk menjelaskan konsep Hak Pengelolaan Perikanan (HPP), yang berpotensi diterapkan sebagai alat pengelolaan perikanan termasuk yang berada dekat pantai di Indonesia untuk mengatasi masalah perikanan open access. Metoda qualitative content analysis yang ditriangulasi melalui diskusi kelompok terfokus melibatkan para ahli, pengambil keputusan dan praktisi, digunakan untuk menjelaskan konsep HPP di Indonesia. Hasilnya menunjukkan bahwa pendekatan pengelolaan HPP melegitimasi entitas pemegang HPP mengamankan kesempatannya menangkap ikan secara ekslusif dengan mencegah pihak lain mengeksploitasi sumber daya ikan secara berlebihan. Pembelajaran dari negara lain menunjukkan bahwa HPP yang diintegrasikan kedalam kerangka rencana pengelolaan perikanan, bisa mengatasi permasalahan perikanan open access, karena mampu meredam motivasi dan tindakan nelayan dalam melakukan perlombaan menangkap ikan. Penggunaan ilmu pengetahuan kontemporer dan kearifan lokal dalam menentukan batasan tangkapan lestari dibarengi dengan upaya pemantauan dan penegakan aturan menentukan keberhasilan penerapannya. Terlihat juga bahwa praktek tradisional seperti Sasi di Maluku yang dimungkinkan oleh adanya pengakuan hak ulayat ‘petuanan laut’ merupakan konsep pemanfaatan sumber daya alam secara eksklusif yang selaras dengan esensi dari HPP. Direkomendasikan agar model pengelolaan berbasis HPP ini dilegitimasi kedalam peraturan perundang-undangan, termasuk Undang-Undang Perikanan Republik Indonesia. The existing management measures of Indonesian fisheries has not yet successfully resolved the overfishing. Fishers are still motivated to race for fish resources as typically occurs in an open access fisheries. This circumstance must be addressed immediately to prevent fisheries collapse. This research aims to describe a concept of Fisheries Management Rights (FMRs) as a management tool. This concept is potentially applicable in Indonesia, especially for near-shore fisheries. A qualitative content analysis method, triangulated through focus group discussions that involved experts, decision makers and practitioners was used to describe FMRs concept. The results indicated that this approach legitimizes the entities of the right holders to secure their exploitation right and to prevent others from over exploiting their fisheries resources. Lessons learnt from other countries showed that this approach that have been  integrated within fisheries management plan, successfully addressed open access problem as it prevents fishers’ motivation to the race for fish. This approach need the contemporary and traditional sciences to inform allowable catch to ensure the success implementation. For instance, “Sasi”, traditional fishing right in Maluku  is have similar framework with the contemporary FMRs. Therefore, FMRs should be acknowledged and adopted into Indonesian’ regulations to prevent the over-exploitatio

Preliminary estimates of the abundance and fidelity of dolphins associating with a demersal trawl fishery

The incidental capture of wildlife in fishing gear presents a global conservation challenge. As a baseline to inform assessments of the impact of bycatch on bottlenose dolphins (Tursiops truncatus) interacting with an Australian trawl fishery, we conducted an aerial survey to estimate dolphin abundance across the fishery. Concurrently, we carried out boat-based dolphin photo-identification to assess short-term fidelity to foraging around trawlers, and used photographic and genetic data to infer longer-term fidelity to the fishery. We estimated abundance at approximate to 2,300 dolphins (95% CI = 1,247-4,214) over the ≈ 25,880-km2 fishery. Mark-recapture estimates yielded 226 (SE = 38.5) dolphins associating with one trawler and some individuals photographed up to seven times over 12 capture periods. Moreover, photographic and genetic re-sampling over three years confirmed that some individuals show longterm fidelity to trawler-associated foraging. Our study presents the first abundance estimate for any Australian pelagic dolphin community and documents individuals associating with trawlers over days, months and years. Without trend data or correction factors for dolphin availability, the impact of bycatch on this dolphin population's conservation status remains unknown. These results should be taken into account by management agencies assessing the impact of fisheries-related mortality on this protected species.Publisher PDFPeer reviewe

Fishers who rely on mangroves: Modelling and mapping the global intensity of mangrove-associated fisheries

Mangroves are critical nursery habitats for fish and invertebrates, providing livelihoods for many coastal communities. Despite their importance, there is currently no estimate of the number of fishers engaged in mangrove associated fisheries, nor on the fishing intensity associated with mangroves at a global scale. We address these gaps by developing a global model of mangrove associated fisher numbers and mangrove fishing intensity. To develop the model, we undertook a three-round Delphi process with mangrove fisheries experts to identify the key drivers of mangrove fishing intensity. We then developed a conceptual model of intensity of mangrove fishing using those factors identified both as being important and for which appropriate global data could be found or developed. These factors were non-urban population, distance to market, distance to mangroves and other fishing grounds, and storm events. By projecting this conceptual model using geospatial datasets, we were able to estimate the number and distribution of mangrove associated fishers and the intensity of fishing in mangroves. We estimate there are 4.1 million mangrove associated fishers globally, with the highest number of mangrove fishers found in Indonesia, India, Bangladesh, Myanmar, and Brazil. Mangrove fishing intensity was greatest throughout Asia, and to a lesser extent West and Central Africa, and Central and South America

Fishers who rely on mangroves: Modelling and mapping the global intensity of mangrove-associated fisheries

Mangroves are critical nursery habitats for fish and invertebrates, providing livelihoods for many coastal communities. Despite their importance, there is currently no estimate of the number of fishers engaged in mangrove associated fisheries, nor on the fishing intensity associated with mangroves at a global scale. We address these gaps by developing a global model of mangrove associated fisher numbers and mangrove fishing intensity. To develop the model, we undertook a three-round Delphi process with mangrove fisheries experts to identify the key drivers of mangrove fishing intensity. We then developed a conceptual model of intensity of mangrove fishing using those factors identified both as being important and for which appropriate global data could be found or developed. These factors were non-urban population, distance to market, distance to mangroves and other fishing grounds, and storm events. By projecting this conceptual model using geospatial datasets, we were able to estimate the number and distribution of mangrove associated fishers and the intensity of fishing in mangroves. We estimate there are 4.1 million mangrove associated fishers globally, with the highest number of mangrove fishers found in Indonesia, India, Bangladesh, Myanmar, and Brazil. Mangrove fishing intensity was greatest throughout Asia, and to a lesser extent West and Central Africa, and Central and South America

The development and use of computer techniques for analysing data on estuarine fish populations

A method of processing data has been developed to facilitate the storage, retrieval and analysis of data collected during ecological studies of fish populations. This method was also used to compare the composition of the fish community in the shallow water of the Peel-Harvey and Swan-Avon estuaries. A total of 42 species representing 22 families were recorded from the Peel-Harvey compared with 50 species and 28 families in the Swan-Avon. Fifteen species accounted for approximately 95% of the total numbers of fish caught in both estuaries. The most prevalent species in the Peel-Harvey was the marine species, Pelates sexlineatus, whose abundance might be related to the presence of large quantities of Cladophora, which constitutes a major proportion of its diet and which is found throughout much of the Peel Inlet. By contrast, the estuarine species, Nematalosa vlaminghi, was the most abundant species in the Swan-Avon in which it utilised both the riverine regions of the upper estuary and also the broad expanses of water in the middle estuary. Amongst the 15 most abundant species, a greater number were represented by populations capable of completing their entire life cycle within the estuary in the Swan-Avon (9) than in the Peel-Harvey (6). The relative abundance of estuarine species was also higher in the Swan-Avon than in the Peel-Harvey. Species richness decreased through the Peel-Harvey but reached a maximum in the middle estuary of the Swan-Avon

Dolphin prey availability and calorific value in an estuarine and coastal environment

Prey density has long been associated with prey profitability for a predator, but prey quality has seldom been quantified. We assessed the potential prey availability and calorific value for Indo-Pacific bottlenose dolphins (Tursiops aduncus) in an estuarine and coastal environment of temperate south-western Australia. Fish were sampled using three methods across three regions (Estuary, Bay and Ocean) in the study area using a 21.5 m beach seine, multi-mesh gillnet, and fish traps. The total biomass and numbers of all species and those of potential dolphin prey were determined in austral summers and winters between 2007 and 2010. The calorific value of 19 species was determined by bomb calorimetry. The aim of the research was to evaluate the significance of prey availability in explaining the higher abundance of dolphins in the region in summer versus winter across years. A higher abundance of prey was captured in the summer (mean of two summer seasons ± 1 SE = 12,080 ± 160) than in the winter (mean of two winter seasons = 7,358 ± 343) using the same number of gear sets in each season and year. In contrast, a higher biomass of potential dolphin prey, of higher energy content, were captured during winters than summers, when fewer dolphins are present in the area. Variability was significant between season and region for the gillnet (p < 0.01), and seine (p < 0.01). The interaction of season and region was also significant for the calorific content captured by the traps (p < 0.03), and between the seasons for biomass of the trap catch (p < 0.02). The dolphin mother and calf pairs that remain in the Estuary and Bay year round may be sustained by the higher quality, and generally larger, if lesser abundant, prey in the winter months. Furthermore, factors such as predator avoidance and mating opportunities are likely to influence patterns of local dolphin abundance. This study provides insights into the complex dynamics of predator – prey interactions, and highlights the importance for a better understanding of prey abundance, distribution and calorific content in explaining the spatial ecology of large apex predators

The populations and community structures of fishes in two large estuaries of south-western Australia

The fish fauna of the large and adjacent Swan and Peel-Harvey estuaries in temperate south-western Australia, were sampled at regular intervals using beach seines, gill nets and otter trawls at a number of sites throughout these systems. A total of 673 037 individuals, representing 38 families and 76 species were caught in the Swan Estuary compared with 144 372 individuals, 29 families and 55 species in the PeelHarvey Estuary. Although the Clupeidae, Terapontidae, Mugilidae, Apogonidae and Atherinidae were the most abundant families in each system, the important species within the families differed between the estuaries. Of the 15 most abundant species in the shallows of the Swan Estuary, seven were marine teleosts which entered the estuary regularly and in large numbers (marine estuarine-opportunists), seven completed their life cycle within the estuary (estuarine) and one (Nematalosa vlaminghi) was anadromous. The contribution of individuals of the marine estuarine-opportunist category to catches in the shallows declined from nearly 95% in the lower estuary, to approximately 17% in the middle estuary and 6% in the upper estuary. The estuarine and anadromous groups together comprised 83 and 94% of the catches in the middle and upper estuaries, respectively. By contrast, marine estuarine-opportunists were the most abundant group in all regions of the Peel-Harvey, including the saline reaches of tributary rivers. The number of species and density of fish in the shallows of the Swan and PeelHarvey systems declined with distance from estuary mouth and rose with increasing salinity and temperature. Classification and ordination of the data from the shallows of both estuarine systems distinguished the ichthyofauna of the saline reaches of the rivers from that of the lower reaches of the estuary. However, the faunal composition of the middle estuary of the Swan was also relatively distinct from those of the lower and upper estuary. The number of species and catch rates in the deeper waters of the Peel-Harvey were influenced to a greater extent by salinity, than those in the shallows. This implies that the larger fish which characterise the deeper waters may thus be less tolerant to low salinities than the smaller fish, typically found in the shallows. Site within the Swan Estuary generally influenced the densities of individual species to a greater extent than either season or year, or the interactions between these factors. When seasonal effects were pronounced, they could be related to summer spawning migrations into the upper estuary (N. vlaminghi, Amniataba caudavittatus ), spring immigrations into the lower estuary (Mugil cephalus ) or winter movements into deeper and more saline waters (Apogon rueppellii ). Marked annual variations in the density of Torquigener pleurogramma were related to large differences in the recruitment of the 0+ age class between years

Cat Gets Its Tern: A Case Study of Predation on a Threatened Coastal Seabird

Domestic cats have a cosmopolitan distribution, commonly residing in urban, suburban and peri-urban environments that are also critical for biodiversity conservation. This study describes the impact of a desexed, free-roaming cat on the behavior of a threatened coastal seabird, the Australian Fairy Tern, Sternula nereis nereis, in Mandurah, south-western Australia. Wildlife cameras and direct observations of cat incursions into the tern colony at night, decapitated carcasses of adult terns, dead, injured or missing tern chicks, and cat tracks and scats around the colony provided strong evidence of cat predation, which led to an initial change in nesting behavior and, ultimately, colony abandonment and the reproductive failure of 111 nests. The death of six breeding terns from the population was a considerable loss for this threatened species and had the potential to limit population growth. This study highlights the significant negative impacts of free-roaming cats on wildlife and the need for monitoring and controlling cats at sites managed for species conservation. It also provides strong evidence against the practice of trap-neuter-release programs and demonstrates that desexed cats can continue to negatively impact wildlife post-release directly through predation, but also indirectly through fundamental changes in prey behavior and a reduction in parental care

Partitioning of food resources among three sympatric scorpionfish (Scorpaeniformes) in coastal waters of the northern Yellow Sea

International audienceThe partitioning of food resources among three abundant co-occurring reef-associated scorpionfish, Hexagrammos agrammus, Hexagrammos otakii and Sebastes schlegelii, was determined on an artificial reef zone in nearshore and offshore coastal waters of northern China, using stomach content and stable isotope analyses (δ13C and δ15N). The three species consumed similar prey items, mainly a variety of crustaceans, teleosts, polychaetes and macroalgae, but the proportions of the items differed among species. The dietary composition of all three scorpionfish differed significantly in nearshore waters, but not between H. otakii and S. schlegelii in offshore waters, where both species fed predominantly on carideans, penaeids and brachyurans. The δ13C values varied significantly among the three scorpionfish in nearshore waters, and tended towards significance (P = 0.053) between H. otakii and S. schlegelii in offshore waters, suggesting that they partition food resources. Bayesian mixing models further confirmed that all scorpionfish were generalist carnivorous and that the main food sources were assimilated in different proportions. In the nearshore waters, resource partitioning occurs among the three scorpionfish, reducing the potential for competition and the feeding ecology implies that they have dietary plasticity, which facilitates their coexistence and maintains local benthic fish community stability