For terrestrial and marine benthic ecologists, landscape ecology provides a framework to address issues of complexity, patchiness, and scale—providing theory and context for ecosystem based management in a changing climate. Marine pelagic ecosystems are likewise changing in response to warming, changing chemistry, and resource exploitation. However, unlike spatial landscapes that migrate slowly with time, pelagic seascapes are embedded in a turbulent, advective ocean. Adaptations from landscape ecology to marine pelagic ecosystem management must consider the nature and scale of biophysical interactions associated with organisms ranging from microbes to whales, a hierarchical organization shaped by physical processes, and our limited capacity to observe and monitor these phenomena across global oceans. High frequency, multiscale, and synoptic characterization of the 4-D variability of seascapes are now available through improved classification methods, a maturing array of satellite remote sensing products, advances in autonomous sampling of multiple levels of biological complexity, and emergence of observational networks. Merging of oceanographic and ecological paradigms will be necessary to observe, manage, and conserve species embedded in a dynamic seascape mosaic, where the boundaries, extent, and location of features change with time.
Over the past 40 years, northwestern Atlantic bluefin tuna (Thunnus thynnus) have experienced high rates of exploitation, targeted fishing on the largest size classes of the population, and an unknown degree of Mediterranean-stock contribution. Lack of recovery despite targeted rebuilding efforts by management prompted an evaluation of the population for changes in age-structure, size-at-age, and stock mixing over three samples (1974–8, 1996–2002, and 2009–14) coinciding with a cycle of exploitation that initially targeted smaller fish, but then showed strong selectivity for the largest and oldest members of the population. Ages and mixing levels were estimated using port- and observer-sampled otoliths collected by the US National Marine Fisheries Service. A comparison of age structure between the 1970s sample and two later samples indicated strong age truncation had occurred, where both mean age (13, 4, and 7 years) and mean length (191, 166, and 159 cm curved fork length) declined among samples. In addition, minor changes in size-at-age were detected among the three samples. Otolith stable isotope analysis indicated fluctuating stock composition, with a substantially higher contribution of Mediterranean-origin fish in the 1990s (48% eastern stock contribution) than in the 1970s (0% contribution) and the most recent sample (4% contribution). Higher mixing and severe age truncation in the 1990s indicated that the northwestern Atlantic population was at a depressed state. Reduced mixing and a slightly expanded age structure in the most recent sample could suggest that recovery has begun. Still, to evaluate the hypothesized cycle of collapse and modest recovery more rigorously, an integrative assessment framework is needed to consider the dynamic nature of stock productivity, trans-oceanic migrations, and fishing selectivity.
We explored alternative status determination criteria and reference points that could simplify fisheries management using a simulated multispecies/ecosystem-based operational management procedure. There are four components to the procedure: (i) limit total removals from the ecosystem; (ii) allocate the total removals limit among aggregate species groups; (iii) maintain individual species above minimum stock size thresholds; and (iv) optimize the species mix (within aggregates) based on bio-economic portfolio analysis. In this procedure, “overfishing” criteria are applied only to aggregates of species at the ecosystem and group level, but “overfished” criteria apply at the species/stock level. Previous work using multispecies production models identified conditions where conservation and yield objectives could be balanced: aggregations of species with similar life histories, species interactions, and responses to environmental forcing supported the highest yields while minimizing risks that individual stocks dropped below biomass thresholds. Here, we use a more complex length structured multispecies, multifleet simulation model to explore management procedure steps (i)–(iii). Different species aggregation rules were applied (single species, functional groups, and full system), and yield curves were constructed for each aggregation level by sequentially increasing effort in each of the fleets (alone and simultaneously), while recruitment for each species varied stochastically around a function based on spawning stock biomass. The performance of individual species and each aggregate type was then compared with respect to yield, biomass, and economic revenue objectives under changing environmental conditions. Our results evaluate the trade-offs between these objectives for the 10 species in the simulated system. Overall we found that there are aggregate catch limits that can both maximize yield and revenue while conserving biomass. However, community composition and revenue trade-off over a range of fishing effort. We consider this a starting point for further development with scientists, managers, fishermen, and other stakeholders in the region.
There is an urgent need for the development of sampling techniques which can provide accurate and precise count, size, and biomass data for fish. This information is essential to support the decision-making processes of fisheries and marine conservation managers and scientists. Digital video technology is rapidly improving, and it is now possible to record long periods of high resolution digital imagery cost effectively, making single or stereo-video systems one of the primary sampling tools. However, manual species identification, counting, and measuring of fish in stereo-video images is labour intensive and is the major disincentive against the uptake of this technology. Automating species identification using technologies developed by researchers in computer vision and machine learning would transform marine science. In this article, a new paradigm of image set classification is presented that can be used to achieve improved recognition rates for a number of fish species. State-of-the-art image set construction, modelling, and matching algorithms from computer vision literature are discussed with an analysis of their application for automatic fish species identification. It is demonstrated that these algorithms have the potential of solving the automatic fish species identification problem in underwater videos captured within unconstrained environments.
The plastic debris contamination, feeding ecology and habitat use of Cynoscion acoupa, an economically important species, were studied in relation to spatial, seasonal and ontogenetic aspects in a tropical estuary. The human impact on the environment was evident in the studied species, reflecting the high contamination of the diet of these fish with plastic debris. Plastic debris is frequently ingested by C. acoupa, regardless of season, area or ontogenetic phase. However, a higher frequency and amount of ingestion suggests that this contaminant might also be acquired through direct consumption and biotransference (from contaminated prey). The ontogenetic phases of C. acoupa utilized different estuarine reaches during seasonal fluctuations. This behaviour was strongly influenced by environmental variables, particularly salinity. During all seasons, juveniles used the upper estuary as shelter to avoid marine predators. However, in the early rainy season, the upper estuary was significantly important as a nursery for this species. The sub-adults used the upper estuary as a feeding ground during the year and migrated to the middle estuary during the late rainy season to avoid osmoregulatory stress. Adults were observed only in the coastal waters of the lower estuary. The trophic guild changed during the ontogeny of C. acoupa, and juveniles primarily fed on plastic debris (FO = 64%), amphipoda (FO = 34%), mysidacea (FO = 17%) and Cathorops spixii (FO = 15%). Sub-adults preferred plastic debris (FO = 50%) and C. spixii (FO = 30%). Both juveniles and sub-adults were classified as opportunistic. Adults were piscivorous, ingesting plastic debris (FO = 100%), C. spixii (FO = 18%), Achirus lineatus(FO = 15%), Stellifer stellifer (FO = 15%) and penaeid shrimp (FO = 15%).
Fisheries managers are increasingly required to develop regulatory frameworks to more effectively manage recreational catches in the marine environment. Although the limitations of conventional controls such as size and bag limits and restricted seasons are recognized, harvest tags that are commonly used to regulate hunting, are rarely applied in marine recreational fisheries. Following overfishing of snapper (Chrysophrys auratus) in Shark Bay, Western Australia, a broad range of management reforms were progressively introduced from 1998 onwards to limit recreational catches and assist stock recovery. Since 2003, these included a harvest tag system in Freycinet Estuary whereby a limited number of harvest tags were made available each year via a ballot. The effectiveness of harvest tags in terms of stock rebuilding and acceptance by recreational fishers was evaluated using: annual phone surveys of all harvest tag recipients between 2011 and 2013; analysis of compliance statistics collected between 2004 and 2015; and interviews with experienced compliance officers. The overall costs of administration and compliance were also assessed. The capacity of harvest tags to successfully constrain the total annual recreational catch contributed to the recovery of the snapper stock in Freycinet Estuary to management target levels within a 10–12 year timeframe. The majority of harvest tag recipients interviewed considered harvest tags were effective in the management of snapper; cost per tag was reasonable; and compliance in the fishery was high. High levels of compliance are essential if harvest tags are to provide a robust management tool to limit total catch and a useful reference frame for angler surveys. Harvest tags have considerable potential with other marine recreational fisheries where catch limits are required to rebuild and sustain valuable but vulnerable fish stocks.
This issue of The State of World Fisheries and Aquaculture aims to provide objective, reliable and up-to-date data and information to a wide range of readers – policy-makers, managers, scientists, stakeholders and indeed all those interested in the fisheries and aquaculture sector. As always, the scope is global and the topics many and varied. This edition uses the latest official statistics on fisheries and aquaculture to present a global analysis of trends in fish stocks, production, processing, utilization, trade and consumption. It also reports on the status of the world’s fishing fleets and analyses the make-up of human engagement in the sector.
The coastal areas are being destroyed due to the usage that effect the natural balance. Unconsciously sand mining from the sea for nearshore nourishment and construction uses are the main ones. Physical interferences for mining of sand cause an ecologic threat to the coastal environment. However, use of marine sand is inevitable because of economic reasons or unobtainable land-based sand resources. The most convenient solution in such a protection–usage dilemma is to reduce negative impacts of sand production from marine. This depends on the accurate determination of criteriaon production place, style, and amount of sand. With this motivation, nearshore geodedic surveying studies performed on Kilyos Campus of Bogazici University located on the Black Sea coast, north of Istanbul, Turkey between 2001-2002. The study area extends 1 km in the longshore. Geodetic survey was carried out in the summer of 2001 to detect the initial condition for the shoreline. Long-term seasonal changes in shoreline positions were determined biannually. The coast was measured with post-processed kinematic GPS.
Besides, shoreline change has studied using Landsat imagery between the years 1986-2015. The data set of Landsat 5 imageries were dated 05.08.1986 and 31.08.2007 and Landsat 7 imageries were dated 21.07.2001 and 28.07.2015. Landcover types in the study area were analyzed on the basis of pixel based classification method. Firstly, unsupervised classification based on ISODATA (Iterative Self Organizing Data Analysis Technique) has been applied and spectral clusters have been determined that gives prior knowledge about the study area. In the second step, supervised classification was carried out by using the three different approaches which are minimum-distance, parallelepiped and maximum-likelihood. All pixel based classification processes were performed with ENVI 4.8 image processing software. Results of geodetic studies and classification outputs will be presented in this paper.
Benthic habitat is defined as ecological environment where marine animals, plants and other organisms live in. Benthic habitat mapping is defined as plotting the distribution and extent of habitats to create a map with complete coverage of the seabed showing distinct boundaries separating adjacent habitats or the use of spatially continuous environmental data sets to represent and predict biological patterns on the seafloor. Seagrass is an essential endemic marine species that prevents coast erosion and regulates carbon dioxide absorption in both undersea and atmosphere. Fishing, mining, pollution and other human activities cause serious damage to seabed ecosystems and reduce benthic biodiversity. According to the latest studies, only 5–10% of the seafloor is mapped, therefore it is not possible to manage resources effectively, protect ecologically important areas. In this study, it is aimed to map seagrass cover using Landsat 8 OLI images in the northern part of Mediterranean coast of Turkey. After pre-processing (e.g. radiometric, atmospheric, water depth correction) of Landsat images, coverage maps are produced with supervised classification using in-situ data which are underwater photos and videos. Result maps and accuracy assessment are presented and discussed.
Abu Dhabi Government endorsed vision for its Maritime Strategy ‘A safe, secure and sustainable maritime domain for Abu Dhabi'. This research study share this vision using the concept of monitoring as tool for marine protection against any possible oil pollution. The best technology to detect and monitor oil pollution and in particularly oil spill is SAR imagery In this case study we chose KOMPSAT-5 SAR.
KOMPSAT-5 carries X-band SAR for earth observation, and is capable of day-and-night imaging under all weather condition. It provides three operation modes: High Resolution Mode to provide 1 m resolution, Standard Mode to provide 3 m resolution and Wide Swath Mode to provide 20 m resolution with 100 km swath at 550 km altitude, with four modes of polarization. KOMPSAT-5 provides products for various applications; security and defense, mapping, and natural resource management, environmental monitoring, disaster monitoring and more. For our case study we chose to work with Wide Swath mode (WS) with Vertical polarization (VV) to cover a wide area of interest located to the north west of Abu Dhabi including some important islands like "Zirku Island", and areas with oil production activities.
The results of data acquired on 4th May 2015 show some spot of oil spill with length estimated about 3 KM, and the daily satellite data acquisition over the period July 24 through July 31 shows serious and many oil spill events some are small, but many others are considered to be big with area size around 20 km2.
In the context of oil spill pollution in the seas, we have to consider the development and increase of overseas transportation, which is an important factor for both social and economic sectors. The harmful effects of marine pollution are numerous, from the damage of marine life to the damage of the aquatic ecosystem as whole. As such, the need for oil slick detection is crucial, for the location of polluted areas and to evaluate slick drift to protect the coastline. Satellite-based oil spill monitoring system now can be used to take precautions and even to determine the possible polluter; it has a vital importance on the detection and protection of national and international waters from the possible damages of petroleum hazard. Finally, and as we suggested in previous studies, we recommend to the national authorities to establish a national near-real time oil spill monitoring system based on SAR satellite imagery, with the support of other tools like AIS and navigation radars.