... Ma. Junemie Hazel L. Lebata, Lewis Le Vay, Jurgenne H. Primavera, Mark E. Walton, and Joseph ... more ... Ma. Junemie Hazel L. Lebata, Lewis Le Vay, Jurgenne H. Primavera, Mark E. Walton, and Joseph B. Biñas ... Figure 4. Annual (A) length-frequency and (B) weight-frequency distributions (%) of Scyllaoli-vacea caught (A) AprilDecember 2002, (B) JanuaryDecember 2003, (C ...
Trabajo presentado en el 23rd Biennial CERF Conference (Grand challenges in coastal and Estuarine... more Trabajo presentado en el 23rd Biennial CERF Conference (Grand challenges in coastal and Estuarine Science: securin our future), celebrado en Portland (Oregon, US) del 8 al 12 de noviembre de 2015.
Trabajo presentado en la 54th Estuarine & Coastal Sciences Association (ECSA 54 Coastal systems u... more Trabajo presentado en la 54th Estuarine & Coastal Sciences Association (ECSA 54 Coastal systems under change: tuning assessments and management tools), celebrada en Sesimbra (Portugal) del 12 al 14 de mayo de 2014.
In order to implement spatial fisheries management in the Arabian Gulf, a better understanding of... more In order to implement spatial fisheries management in the Arabian Gulf, a better understanding of the distribution of fish in relation to benthic habitats is required. To facilitate this, hydroacoustic fish surveys were conducted over oyster bed/reef ("shallow") and surrounding soft sediment ("deep") habitats in the offshore central Gulf, within Qatari waters. Transects at 'shallow' sites had significantly higher mean fish density and biomass. Mean target strength of individual fish was also significantly higher at 'shallow' sites. Fish positions in the water column were examined and overall there was a closer association with the seabed at the 'shallow' sites. Larger fish were found significantly closer to the seabed than smaller fish across all sites, but more so at 'shallow' sites than at 'deep' sites. Acoustic return from the seabed was extracted to provide information on the habitat type both using 'Sonar5' and 'Visual Habitat' software. The different site categories ('shallow' vs 'deep') were significantly different for all the measures of acoustic habitat. Fish density was significantly related to 'Visual Habitat' data, more so than depth alone. Our results show that fish distribution in the offshore Gulf is associated with complex, shallow oyster bed/reef habitats, and this is particularly the case for larger demersal fish that are commercially 2 exploited. The ability to characterise benthic habitats from acoustic fish survey data shows promise, with important time saving implications for the monitoring of marine environments and developing a spatial approach to fisheries management. This may include the identification of habitats with a relatively high density of larger fish for inclusion in candidate marine protected areas.
Trichocorixa verticalis verticalis, a North American water boatman, is the only alien corixid in ... more Trichocorixa verticalis verticalis, a North American water boatman, is the only alien corixid in European fresh waters. It has rapidly spread, becoming the dominant corixid in and around the Doñana protected area in SW Spain. Its high abundance and similar morphology to native corixids suggest that T. verticalis may impact them through competition for food. Here we used stable isotopes of nitrogen (N) and carbon (C) and Bayesian analytical tools to investigate niche partitioning between T. verticalis and the native water boatman Sigara lateralis and Sigara scripta through a combination of experimental and field data. Species sampled from permanent ponds and laboratory aquaria could be separated based on their isotopic values (δ 15 N and δ 13 C). S. lateralis consistently showed higher δ 15 N values than T. verticalis, suggesting that the invasive species may be feeding at a lower trophic position and relying more on herbivory than its native competitors. This was particularly true for the T. verticalis nymph stage, which showed lower δ 15 N values compared to adults, indicating ontogenetic dietary shifts. In contrast, native corixids and the invasive species showed similar isotopic compositions in temporary habitats at different stages in the flooding-desiccation cycle, suggesting some degree of niche overlap and a slight reduction in trophic level for S. lateralis when inhabiting ephemeral systems. The combination of experimental and field data can help elucidate trophic interactions during a biological invasion. Stable isotopes provided insights into the trophic ecology of this invasive species and into the mechanisms facilitating coexistence with native species.
Copyright and moral rights for the publications made accessible in the public portal are retained... more Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
In a restored wetland (South of Spain), where different flow regimes control water exchange 25 wi... more In a restored wetland (South of Spain), where different flow regimes control water exchange 25 with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic 26 counterpart species Palaemon macrodactylus. This controlled macrocosm offers an excellent 27 opportunity to investigate how the effects of water management, through different flow 28 regimes, and the presence of a non-native species affect the aquatic community and the trophic 29 niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. 30 We found that increased water exchange rate (5% day-1 in mixed ponds vs. 0.1% day-1 in 31 extensive ponds) modified the aquatic community of this wetland; while extensive ponds are 32 dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds 33 presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine 34 origin of nutrients and primary production might explain seasonal and spatial differences found 35 among ponds of this wetland. A combined analysis of gut contents and isotopic composition of 36 the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) 37 while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap 38 occurred when both species coexist at mixed ponds where a higher water exchange and high 39 abundance of mysids and copepods diversifies the native species" diet. Thus differences in the 40 trophic ecology of both species are clearly explained by water management. This experimental 41 study is a valuable tool for integrated management between river basin and wetlands since it 42 allows quantification of wetland community changes in response to the flow regime. 43 44 45 46 49 Arthington, 2002; González-Ortegón et al., 2012), and closed systems such as wetlands are the 50 easiest systems in which to determine aquatic community responses to any perturbation 51 (Scheffer and van Nes, 2004). Water regulation modifies hydrological factors and 52 physicochemical conditions, influencing biological production (bottom up control) and the 53 aquatic assemblage structure (Poff and Allan, 1995; González-Ortegón and Drake, 2012). The 54 impacts of flow change have been described across broad taxonomic groups in plants, 55 invertebrates and fish (Fausch and Bramblett, 1991; Poff and Allan, 1995) and in food web 56 structure due to alternative basal resources available for consumers (Wantzen et al., 2002; 57 González-Ortegón et al., 2010; Wang et al., 2011). In addition, the alteration of flow regimes 58 can facilitate the invasion and success of non-native species (Bunn and Arthinghton, 2002). In 59 this way, after successful establishment of an exotic species in the new habitat, its effects on 60 native species may have diverse intensities, ranging from an apparently non-competitive 61 coexistence with the native counterpart (González-Ortegón et al., 2010) to the extinction of 62 native species (Clavero and Garcia-Berthou, 2005). 63 Food web studies are central in understanding changes in community organisation and 64 ecosystem functioning since they incorporate the ecological interactions of that ecosystem in 65 an integrated way (Sierszen et al., 2006; Pace et al., 2013). The study of food webs requires 66 detailed work of the composition and density of each of the aquatic components and the 67 relationships among each component based on gut contents. However, the diversity in primary 68 producers, the complex mobility of consumers, and the digestion of prey in the stomach can 69 make it difficult to ascertain trophic relations among species in an ecosystem (González-70 Ortegón et al., 2010; Wang et al., 2011). The use of stable carbon and nitrogen isotope ratios (δ 76 dynamics (Kingsford 2000; Coll et al., 2011).The reconstructed wetlands of Veta La Palma (on 77 the west bank of the Guadalquivir estuary, SW Spain), that are used for extensive and semi-78 extensive aquaculture by regulating water exchange with the Guadalquivir estuary, offer an 79 excellent opportunity for testing how water regulation influences species composition in the 80 aquatic community. Water flow from the estuary allows for recruitment of the non-native 81 species P. macrodactylus Rathbun, 1902 (Gonzalez-Ortegón et al., 2010) and this introduced 82 species (Lejeusne et al., 2014) may compete with the native counterpart species Palaemon 83 varians (Leach, 1814) within the Veta La Palma wetland. 84 This study explores how water flow management in reconstructed wetlands and the 85 introduction of the non-native shrimp P. macrodactylus determine aquatic community 86 composition and influence the trophic niche of the native P. varians. We estimated density of 87 aquatic fauna, studied gut contents of both shrimps species and analysed food web faunal and 88 source samples seasonally and in individual ponds using isotope mixing models. We 89 hypothesised that different water exchange rates could lead to shifts in the community structure 90 and affect the type of food resources consumed by the two shrimps species in the food webs of 91 the wetland. Secondarily, the density and feeding habits of the native species Palaemon 92 varians should be affected mainly by the introduction of the non-native species Palaemon 93 macrodactylus. 94 95 96 MATERIAL AND METHODS In the 3000 ha of reconstructed wetlands at Veta La Palma (VP) two pond management 98 systems are operated (Fig. 1). In mixed ponds, water enters a row of smaller ponds (0.6 ha 99 each) where semi-extensive aquaculture is performed prior to entering the large 70 ha 100 extensive aquaculture ponds; here water flow rates are higher, resulting in a exchange rate in 101 the extensive ponds of 5% day-1. In purely extensive aquaculture ponds, with no prior 102 aquaculture activity, water exchange rates are 0.1% day-1. Water exchange occurs daily during 103 the year, with the exception of the period between November and February. The differences in 104 water exchanges rates between mixed and extensive pond determined the spatial and temporal 105 salinity patterns in these two pond systems (Fig. 2). Three mixed pond systems (A3, B3 and 106 A5) and two purely extensive ponds (A7 and B7) were seasonally sampled 4 times (1-4 May
Extensive aquaculture in coastal and estuarine wetlands can support both increased food productio... more Extensive aquaculture in coastal and estuarine wetlands can support both increased food production and wider ecosystem services when underpinned by effective management to promote productivity and hence food webs that support both commercial species and biodiversity. Changing hydrology, specifically water movement, within wetlands significantly impacts the physico-chemical properties of the water body and hence can be employed to manipulate productivity and alter patterns of recruitment of commercial species and may also transfer non-native species from the supplying water bodies. The reconstructed wetlands of Veta la Palma in the Doñana Natural Park are subjected to either a 1 % or 5 % d -1 water exchange with water drawn from the adjacent Guadalquivir estuary. This site provides an excellent opportunity for examining the effect of water management on the food webs that support both the birdlife and aquaculture activities for which this habitat is managed. Stable isotopes were used to examine food webs in three replicate lagoons under each water management scheme. In lagoons receiving higher water exchange, phytoplankton productivity appeared to be more important than benthic production in supporting food webs. Increased water exchange also changed the shape of the food webs, facilitated the colonisation of at least one non-native species and increased the importance of non-native species in the diets of large commercially harvested fish (> 60 % of seabass diet). Lagoons with high water flows also had between three and four times greater shrimp biomass than those of low flow lagoons. Non-native fauna were opportunistic omnivores, eating marginally more non-natives in lagoons with greater water exchange. Overall non-native cordgrass Spartina densiflora contributed only slightly more to food webs compared with the native reed Phragmites australis, despite the lagoon edge occupancy ratio of 9:1, respectively. Nonnatives also appear to enhance food provision for large predators and wetland birds, by increasing biomass, without competing for resources with native species, supporting the dual management objectives of aquaculture and waterbird conservation.
Copyright and moral rights for the publications made accessible in the public portal are retained... more Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
The lack of space and opportunity for development have been identified as key reasons behind the ... more The lack of space and opportunity for development have been identified as key reasons behind the stagnation of the European aquaculture industry. With the historical loss and degradation of current European wetlands there is an opportunity for harnessing the commercial investment of the aquaculture industry in construction of dual purpose wetlands that incorporate both conservation and extensive aquaculture activities. These wetlands can be used to expand the area available to suitable aquaculture into ecologically sensitive areas, such as Natura 2000 sites. Veta la Palma (VLP) situated in the Doñana Natural Park (and a Natura 2000 site) is an example of such an aquaculture development and a possible model for future opportunities. In the current study some of the important ecosystem services that are provided by VLP are assessed. The provisioning services of VLP were the economic rationale for the investment and more than 820 tonnes yr-1 of fish and shrimp is produced, through a mixture of semi-extensive and extensive aquaculture. The regulating services include nutrient absorption, and the flow of river water through VLP and high primary production results in the absorption of 377 tonnes of dissolved inorganic nitrogen yr-1 , and 516 tonnes of C yr-1. Supporting services include the provision of habitat for more than 94 bird and 21 fish species. The primary production that supports the birds, extensive and semiextensive aquaculture production was also estimated to be 167,000 t, 50,000 t and 133,000 t yr-1 , respectively. The losses to birds are substantial and these estimates indicate that almost half of the primary production supports the wetland birds which directly consume 249 tonnes of fish and 2578 tonnes of invertebrates per annum. However it is the ecological credentials of the farm that enable premium prices and hence ensure the economic viability of the farm. The study demonstrates the possibility of using aquaculture to mitigate the historical loss of wetlands, provide significant ecosystem services and contribute to achievement of the European environmental legislative goals, and furthers the opportunity for the expansion of aquaculture into sensitive but impacted habitats.
Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively ... more Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively fished throughout their range in the Indo-West Pacific. Despite this high level of exploitation very little is known about the population dynamics of any of the Scylla species. The present study concentrated on an exploited population of Scylla paramamosain in a natural estuarine mangrove on Can Coc Island in the mouth of the Hau River, Mekong Delta, Vietnam. A total of 6,114 juvenile crabs captured on the seaward mangrove fringe were internally tagged by injection of coded microwire tags and released over a period of 29 days. Recaptures were monitored over the following 144 days. There was little migratory movement within the estuary; of 285 recaptured crabs, 93% were recovered within the island mangrove study area and only two individuals were recovered from mangroves lining the opposite mainland riverbanks. A von Bertalanffy growth function was fitted to growth increment data from recaptured crabs, with L max = 150 mm to derive a growth constant, k = 2.39 year -1 . The theoretical age at which carapace width is zero (t 0 ) was derived from known size at recruitment at instar 1, giving a value of -0.0095 years. Previous studies of the same population have shown that female S. paramamosain reach maturity at a mean size of 102 mm carapace width. The present study indicates that they attain this size at around 160 days from first settlement in the mangrove fringe. Abundance of juvenile crabs in the study area was estimated by the Petersen method as 1,101,500 (95% CI 4,17,300-1,785,800, representing 1,102 crabs ha -1 of mangrove. Estimation of mortality from tag returns and from the age-catch curves during a period of constant recruitment were comparable (Z = 1.11 and 1.04 month -1 , respectively). Fishing only accounted for 14% of total mortality, suggesting that at the time exploitation was not at a critical level despite the apparent high level of fishing activity. Communicated by A. Atkinson, Cambridge.
Supplement. Further details of the δ 13 C and δ 15 N values of samples from the 3 sample location... more Supplement. Further details of the δ 13 C and δ 15 N values of samples from the 3 sample locations in each habitat (see Table 1 in the main article)
Over the last decade, hatchery production of mud crabs has become technically and economically mo... more Over the last decade, hatchery production of mud crabs has become technically and economically more feasible, enabling evaluation of the potential effectiveness of hatchery release in fisheries enhancement. The high growth rates and limited movement of ...
Ranching, stock enhancement and restocking are management approaches involving the release of wil... more Ranching, stock enhancement and restocking are management approaches involving the release of wild or hatchery-bred organisms to enhance, conserve or restore fisheries. The present study, conducted from April 2002 to November 2005, evaluated the effectiveness of releasing wild and hatchery-reared (HR) mud crabs in the mangroves of Ibajay, Aklan, Philippines where preliminary studies demonstrated declining fishery yields, abundance and size of crabs. Comparison of survival and growth of wild-released and HR Scylla olivacea and HR Scylla serrata demonstrated the effect of nursery conditioning, size-at-release and species differences. Overall yield and catch per unit effort (CPUE) increased by 46% after stock enhancement trials. Recapture rates of released crabs were highest in wild-released S. olivacea and in crabs measuring 65.0–69.9 mm carapace width (CW) and lowest in non-conditioned HR S. serrata. Growth rates were highest for conditioned HR S. olivacea and lowest for conditioned HR S. serrata (11.7 and 3.7 mm month–1 respectively). Fishing mortality was highest for S. olivacea, whereas natural mortality was greater for S. serrata. Conditioning hatchery-bred animals before release is also important in obtaining higher survival. S. olivacea was the more appropriate of the two species for release in mangrove habitats inundated with low-salinity water. However, there is a need for site-specific studies to evaluate the effectiveness of releases.
Brackishwater pond culture has been a major factor in mangrove loss in Southeast Asia, hence, the... more Brackishwater pond culture has been a major factor in mangrove loss in Southeast Asia, hence, the need to develop environment-friendly technologies such as mud crab Scylla (Portunidae) culture in mangrove pens exists. This study evaluated the e¡ects of mud crab netpen systems in central Philippines on mangrove macro£ora, and the replacement of dietary ¢sh with low-cost pellets.Wild or hatchery-sourced Scylla olivacea and Scylla serrata were stocked at 0.50 .8 m À 2 in 167^200 m 2 nylon netpens (2.3 cm stretched mesh) in Avicennia-dominated mangrove habitats. The feeding treatments were: (A) Zarraga: (1) no feeding (natural productivity), (2) no feeding for 1 month1supplementary feeding, (3) ¢sh biomass and (4) low-cost pellets, and (B) Batan: (1) ¢sh biomass and (2) pellets1¢sh biomass. Feeds were given ad libitum twice daily. Growth and survival rates of S. olivacea in Zarraga pens were not signi¢cantly different among treatments, although crabs fed ¢sh biomass had the highest survival, body weight and production. Similarly, growth and survival of S. serrata were not signi¢cantly di¡erent between the Batan treatments. Economic analysis of the latter gave a 38.5% return on investment (ROI) and 2.6 years payback period (PP) for pellets1¢sh biomass treatment compared with 27.5% ROI and 3.6 years PP for ¢sh alone. Sensitivity analysis showed an improved economic performance of the pellets1¢sh biomass treatment by increasing the survival rate. Evaluation of mangrove community structure showed that crab culture reduced species diversity, numbers and biomass of seedlings and saplings, but not of mangrove trees. Therefore, mud crab pen culture is recommended for mangrove sites with mature trees, but not seedlings and saplings, and low-cost pellets can reduce dependence on ¢sh biomass.
Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively ... more Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively fished throughout their range in the Indo-West Pacific. Despite this high level of exploitation very little is known about the population dynamics of any of the Scylla species. The present study concentrated on an exploited population of Scylla paramamosain in a natural estuarine mangrove on Can Coc Island in the mouth of the Hau River, Mekong Delta, Vietnam. A total of 6,114 juvenile crabs captured on the seaward mangrove fringe were internally tagged by injection of coded microwire tags and released over a period of 29 days. Recaptures were monitored over the following 144 days. There was little migratory movement within the estuary; of 285 recaptured crabs, 93% were recovered within the island mangrove study area and only two individuals were recovered from mangroves lining the opposite mainland riverbanks. A von Bertalanffy growth function was fitted to growth increment data from recaptured crabs, with L max = 150 mm to derive a growth constant, k = 2.39 year-1. The theoretical age at which carapace width is zero (t 0) was derived from known size at recruitment at instar 1, giving a value of-0.0095 years. Previous studies of the same population have shown that female S. paramamosain reach maturity at a mean size of 102 mm carapace width. The present study indicates that they attain this size at around 160 days from first settlement in the mangrove fringe. Abundance of juvenile crabs in the study area was estimated by the Petersen method as 1,101,500 (95% CI 4,17,300-1,785,800, representing 1,102 crabs ha-1 of mangrove. Estimation of mortality from tag returns and from the age-catch curves during a period of constant recruitment were comparable (Z = 1.11 and 1.04 month-1 , respectively). Fishing only accounted for 14% of total mortality, suggesting that at the time exploitation was not at a critical level despite the apparent high level of fishing activity. Communicated by A. Atkinson, Cambridge.
Offspring size variation in relation to maternal size and season is characteristic of a range of ... more Offspring size variation in relation to maternal size and season is characteristic of a range of species living in seasonal environments. Little is known about the proximate mechanisms explaining the links between maternally driven variation in offspring phenotypes, for instance when mothers have different diets depending on their size or the season. Here, we use stable isotopes techniques to quantify size dependent and seasonal variations in diet in mothers of shrimp Palaemon serratus and explore possible links between maternal diet and phenotype of embryos and freshly hatched larvae. We found that larger females, which occur more frequently in winter, produce larvae with higher carbon and nitrogen content as well as higher percent carbon, than smaller mothers collected in winter. In addition, isotopic composition suggest that larger mothers collected in winter, were feeding at a higher trophic level, or on an enriched prey pool compared with smaller mothers collected in summer. Ov...
Journal of the Korean Society For Marine Environment Energy, 2010
The paper describes the objectives of Yellow Sea Large Marine Ecosystem (YSLME) project, focusing... more The paper describes the objectives of Yellow Sea Large Marine Ecosystem (YSLME) project, focusing on procedural and practical aspects. YSLME is a highly productive sea yet possibly one of the most impacted large marine ecosystems, in terms of anthropogenic stressors, due the enormous coastal population. The aim of the YSLME project is the reduction of ecosystem stress through identification of the environmental problems in the Transboundary Diagnostic Analysis (TDA) that are then addressed in the Strategic Action Programme (SAP). One of the major problems found to be affecting biological diversity is habitat modification through wetland reclamation, conversion and degradation. Since the early 1900's more than 40% of intertidal wetlands have been reclaimed in Korea, and 60% of Chinese coastal wetlands have been converted or reclaimed. Damaging fishing practices, pollution and coastal eutrophication have further degraded the coastal environment reducing the biological diversity. To combat this loss, the YSLME project has mounted a public awareness campaign to raise environmental consciousness targeted at all different levels of society, from politicians at parliamentary workshops, local government officer training events, scientific conferences and involvement of scientists in the project research and reporting, to university and high school students in our visiting internship programmes and environmental †
... Ma. Junemie Hazel L. Lebata, Lewis Le Vay, Jurgenne H. Primavera, Mark E. Walton, and Joseph ... more ... Ma. Junemie Hazel L. Lebata, Lewis Le Vay, Jurgenne H. Primavera, Mark E. Walton, and Joseph B. Biñas ... Figure 4. Annual (A) length-frequency and (B) weight-frequency distributions (%) of Scyllaoli-vacea caught (A) AprilDecember 2002, (B) JanuaryDecember 2003, (C ...
Trabajo presentado en el 23rd Biennial CERF Conference (Grand challenges in coastal and Estuarine... more Trabajo presentado en el 23rd Biennial CERF Conference (Grand challenges in coastal and Estuarine Science: securin our future), celebrado en Portland (Oregon, US) del 8 al 12 de noviembre de 2015.
Trabajo presentado en la 54th Estuarine & Coastal Sciences Association (ECSA 54 Coastal systems u... more Trabajo presentado en la 54th Estuarine & Coastal Sciences Association (ECSA 54 Coastal systems under change: tuning assessments and management tools), celebrada en Sesimbra (Portugal) del 12 al 14 de mayo de 2014.
In order to implement spatial fisheries management in the Arabian Gulf, a better understanding of... more In order to implement spatial fisheries management in the Arabian Gulf, a better understanding of the distribution of fish in relation to benthic habitats is required. To facilitate this, hydroacoustic fish surveys were conducted over oyster bed/reef ("shallow") and surrounding soft sediment ("deep") habitats in the offshore central Gulf, within Qatari waters. Transects at 'shallow' sites had significantly higher mean fish density and biomass. Mean target strength of individual fish was also significantly higher at 'shallow' sites. Fish positions in the water column were examined and overall there was a closer association with the seabed at the 'shallow' sites. Larger fish were found significantly closer to the seabed than smaller fish across all sites, but more so at 'shallow' sites than at 'deep' sites. Acoustic return from the seabed was extracted to provide information on the habitat type both using 'Sonar5' and 'Visual Habitat' software. The different site categories ('shallow' vs 'deep') were significantly different for all the measures of acoustic habitat. Fish density was significantly related to 'Visual Habitat' data, more so than depth alone. Our results show that fish distribution in the offshore Gulf is associated with complex, shallow oyster bed/reef habitats, and this is particularly the case for larger demersal fish that are commercially 2 exploited. The ability to characterise benthic habitats from acoustic fish survey data shows promise, with important time saving implications for the monitoring of marine environments and developing a spatial approach to fisheries management. This may include the identification of habitats with a relatively high density of larger fish for inclusion in candidate marine protected areas.
Trichocorixa verticalis verticalis, a North American water boatman, is the only alien corixid in ... more Trichocorixa verticalis verticalis, a North American water boatman, is the only alien corixid in European fresh waters. It has rapidly spread, becoming the dominant corixid in and around the Doñana protected area in SW Spain. Its high abundance and similar morphology to native corixids suggest that T. verticalis may impact them through competition for food. Here we used stable isotopes of nitrogen (N) and carbon (C) and Bayesian analytical tools to investigate niche partitioning between T. verticalis and the native water boatman Sigara lateralis and Sigara scripta through a combination of experimental and field data. Species sampled from permanent ponds and laboratory aquaria could be separated based on their isotopic values (δ 15 N and δ 13 C). S. lateralis consistently showed higher δ 15 N values than T. verticalis, suggesting that the invasive species may be feeding at a lower trophic position and relying more on herbivory than its native competitors. This was particularly true for the T. verticalis nymph stage, which showed lower δ 15 N values compared to adults, indicating ontogenetic dietary shifts. In contrast, native corixids and the invasive species showed similar isotopic compositions in temporary habitats at different stages in the flooding-desiccation cycle, suggesting some degree of niche overlap and a slight reduction in trophic level for S. lateralis when inhabiting ephemeral systems. The combination of experimental and field data can help elucidate trophic interactions during a biological invasion. Stable isotopes provided insights into the trophic ecology of this invasive species and into the mechanisms facilitating coexistence with native species.
Copyright and moral rights for the publications made accessible in the public portal are retained... more Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
In a restored wetland (South of Spain), where different flow regimes control water exchange 25 wi... more In a restored wetland (South of Spain), where different flow regimes control water exchange 25 with the adjacent Guadalquivir estuary, the native Palaemon varians coexists with an exotic 26 counterpart species Palaemon macrodactylus. This controlled macrocosm offers an excellent 27 opportunity to investigate how the effects of water management, through different flow 28 regimes, and the presence of a non-native species affect the aquatic community and the trophic 29 niche (by gut contents and C-N isotopic composition) of the native shrimp Palaemon varians. 30 We found that increased water exchange rate (5% day-1 in mixed ponds vs. 0.1% day-1 in 31 extensive ponds) modified the aquatic community of this wetland; while extensive ponds are 32 dominated by isopods and amphipods with low presence of P. macrodactylus, mixed ponds 33 presented high biomass of mysids, corixids, copepods and both shrimp species. An estuarine 34 origin of nutrients and primary production might explain seasonal and spatial differences found 35 among ponds of this wetland. A combined analysis of gut contents and isotopic composition of 36 the native and the exotic species showed that: (1) native P. varians is mainly omnivorous (2) 37 while the non-native P. macrodactylus is more zooplanktivorous and (3) a dietary overlap 38 occurred when both species coexist at mixed ponds where a higher water exchange and high 39 abundance of mysids and copepods diversifies the native species" diet. Thus differences in the 40 trophic ecology of both species are clearly explained by water management. This experimental 41 study is a valuable tool for integrated management between river basin and wetlands since it 42 allows quantification of wetland community changes in response to the flow regime. 43 44 45 46 49 Arthington, 2002; González-Ortegón et al., 2012), and closed systems such as wetlands are the 50 easiest systems in which to determine aquatic community responses to any perturbation 51 (Scheffer and van Nes, 2004). Water regulation modifies hydrological factors and 52 physicochemical conditions, influencing biological production (bottom up control) and the 53 aquatic assemblage structure (Poff and Allan, 1995; González-Ortegón and Drake, 2012). The 54 impacts of flow change have been described across broad taxonomic groups in plants, 55 invertebrates and fish (Fausch and Bramblett, 1991; Poff and Allan, 1995) and in food web 56 structure due to alternative basal resources available for consumers (Wantzen et al., 2002; 57 González-Ortegón et al., 2010; Wang et al., 2011). In addition, the alteration of flow regimes 58 can facilitate the invasion and success of non-native species (Bunn and Arthinghton, 2002). In 59 this way, after successful establishment of an exotic species in the new habitat, its effects on 60 native species may have diverse intensities, ranging from an apparently non-competitive 61 coexistence with the native counterpart (González-Ortegón et al., 2010) to the extinction of 62 native species (Clavero and Garcia-Berthou, 2005). 63 Food web studies are central in understanding changes in community organisation and 64 ecosystem functioning since they incorporate the ecological interactions of that ecosystem in 65 an integrated way (Sierszen et al., 2006; Pace et al., 2013). The study of food webs requires 66 detailed work of the composition and density of each of the aquatic components and the 67 relationships among each component based on gut contents. However, the diversity in primary 68 producers, the complex mobility of consumers, and the digestion of prey in the stomach can 69 make it difficult to ascertain trophic relations among species in an ecosystem (González-70 Ortegón et al., 2010; Wang et al., 2011). The use of stable carbon and nitrogen isotope ratios (δ 76 dynamics (Kingsford 2000; Coll et al., 2011).The reconstructed wetlands of Veta La Palma (on 77 the west bank of the Guadalquivir estuary, SW Spain), that are used for extensive and semi-78 extensive aquaculture by regulating water exchange with the Guadalquivir estuary, offer an 79 excellent opportunity for testing how water regulation influences species composition in the 80 aquatic community. Water flow from the estuary allows for recruitment of the non-native 81 species P. macrodactylus Rathbun, 1902 (Gonzalez-Ortegón et al., 2010) and this introduced 82 species (Lejeusne et al., 2014) may compete with the native counterpart species Palaemon 83 varians (Leach, 1814) within the Veta La Palma wetland. 84 This study explores how water flow management in reconstructed wetlands and the 85 introduction of the non-native shrimp P. macrodactylus determine aquatic community 86 composition and influence the trophic niche of the native P. varians. We estimated density of 87 aquatic fauna, studied gut contents of both shrimps species and analysed food web faunal and 88 source samples seasonally and in individual ponds using isotope mixing models. We 89 hypothesised that different water exchange rates could lead to shifts in the community structure 90 and affect the type of food resources consumed by the two shrimps species in the food webs of 91 the wetland. Secondarily, the density and feeding habits of the native species Palaemon 92 varians should be affected mainly by the introduction of the non-native species Palaemon 93 macrodactylus. 94 95 96 MATERIAL AND METHODS In the 3000 ha of reconstructed wetlands at Veta La Palma (VP) two pond management 98 systems are operated (Fig. 1). In mixed ponds, water enters a row of smaller ponds (0.6 ha 99 each) where semi-extensive aquaculture is performed prior to entering the large 70 ha 100 extensive aquaculture ponds; here water flow rates are higher, resulting in a exchange rate in 101 the extensive ponds of 5% day-1. In purely extensive aquaculture ponds, with no prior 102 aquaculture activity, water exchange rates are 0.1% day-1. Water exchange occurs daily during 103 the year, with the exception of the period between November and February. The differences in 104 water exchanges rates between mixed and extensive pond determined the spatial and temporal 105 salinity patterns in these two pond systems (Fig. 2). Three mixed pond systems (A3, B3 and 106 A5) and two purely extensive ponds (A7 and B7) were seasonally sampled 4 times (1-4 May
Extensive aquaculture in coastal and estuarine wetlands can support both increased food productio... more Extensive aquaculture in coastal and estuarine wetlands can support both increased food production and wider ecosystem services when underpinned by effective management to promote productivity and hence food webs that support both commercial species and biodiversity. Changing hydrology, specifically water movement, within wetlands significantly impacts the physico-chemical properties of the water body and hence can be employed to manipulate productivity and alter patterns of recruitment of commercial species and may also transfer non-native species from the supplying water bodies. The reconstructed wetlands of Veta la Palma in the Doñana Natural Park are subjected to either a 1 % or 5 % d -1 water exchange with water drawn from the adjacent Guadalquivir estuary. This site provides an excellent opportunity for examining the effect of water management on the food webs that support both the birdlife and aquaculture activities for which this habitat is managed. Stable isotopes were used to examine food webs in three replicate lagoons under each water management scheme. In lagoons receiving higher water exchange, phytoplankton productivity appeared to be more important than benthic production in supporting food webs. Increased water exchange also changed the shape of the food webs, facilitated the colonisation of at least one non-native species and increased the importance of non-native species in the diets of large commercially harvested fish (> 60 % of seabass diet). Lagoons with high water flows also had between three and four times greater shrimp biomass than those of low flow lagoons. Non-native fauna were opportunistic omnivores, eating marginally more non-natives in lagoons with greater water exchange. Overall non-native cordgrass Spartina densiflora contributed only slightly more to food webs compared with the native reed Phragmites australis, despite the lagoon edge occupancy ratio of 9:1, respectively. Nonnatives also appear to enhance food provision for large predators and wetland birds, by increasing biomass, without competing for resources with native species, supporting the dual management objectives of aquaculture and waterbird conservation.
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The lack of space and opportunity for development have been identified as key reasons behind the ... more The lack of space and opportunity for development have been identified as key reasons behind the stagnation of the European aquaculture industry. With the historical loss and degradation of current European wetlands there is an opportunity for harnessing the commercial investment of the aquaculture industry in construction of dual purpose wetlands that incorporate both conservation and extensive aquaculture activities. These wetlands can be used to expand the area available to suitable aquaculture into ecologically sensitive areas, such as Natura 2000 sites. Veta la Palma (VLP) situated in the Doñana Natural Park (and a Natura 2000 site) is an example of such an aquaculture development and a possible model for future opportunities. In the current study some of the important ecosystem services that are provided by VLP are assessed. The provisioning services of VLP were the economic rationale for the investment and more than 820 tonnes yr-1 of fish and shrimp is produced, through a mixture of semi-extensive and extensive aquaculture. The regulating services include nutrient absorption, and the flow of river water through VLP and high primary production results in the absorption of 377 tonnes of dissolved inorganic nitrogen yr-1 , and 516 tonnes of C yr-1. Supporting services include the provision of habitat for more than 94 bird and 21 fish species. The primary production that supports the birds, extensive and semiextensive aquaculture production was also estimated to be 167,000 t, 50,000 t and 133,000 t yr-1 , respectively. The losses to birds are substantial and these estimates indicate that almost half of the primary production supports the wetland birds which directly consume 249 tonnes of fish and 2578 tonnes of invertebrates per annum. However it is the ecological credentials of the farm that enable premium prices and hence ensure the economic viability of the farm. The study demonstrates the possibility of using aquaculture to mitigate the historical loss of wetlands, provide significant ecosystem services and contribute to achievement of the European environmental legislative goals, and furthers the opportunity for the expansion of aquaculture into sensitive but impacted habitats.
Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively ... more Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively fished throughout their range in the Indo-West Pacific. Despite this high level of exploitation very little is known about the population dynamics of any of the Scylla species. The present study concentrated on an exploited population of Scylla paramamosain in a natural estuarine mangrove on Can Coc Island in the mouth of the Hau River, Mekong Delta, Vietnam. A total of 6,114 juvenile crabs captured on the seaward mangrove fringe were internally tagged by injection of coded microwire tags and released over a period of 29 days. Recaptures were monitored over the following 144 days. There was little migratory movement within the estuary; of 285 recaptured crabs, 93% were recovered within the island mangrove study area and only two individuals were recovered from mangroves lining the opposite mainland riverbanks. A von Bertalanffy growth function was fitted to growth increment data from recaptured crabs, with L max = 150 mm to derive a growth constant, k = 2.39 year -1 . The theoretical age at which carapace width is zero (t 0 ) was derived from known size at recruitment at instar 1, giving a value of -0.0095 years. Previous studies of the same population have shown that female S. paramamosain reach maturity at a mean size of 102 mm carapace width. The present study indicates that they attain this size at around 160 days from first settlement in the mangrove fringe. Abundance of juvenile crabs in the study area was estimated by the Petersen method as 1,101,500 (95% CI 4,17,300-1,785,800, representing 1,102 crabs ha -1 of mangrove. Estimation of mortality from tag returns and from the age-catch curves during a period of constant recruitment were comparable (Z = 1.11 and 1.04 month -1 , respectively). Fishing only accounted for 14% of total mortality, suggesting that at the time exploitation was not at a critical level despite the apparent high level of fishing activity. Communicated by A. Atkinson, Cambridge.
Supplement. Further details of the δ 13 C and δ 15 N values of samples from the 3 sample location... more Supplement. Further details of the δ 13 C and δ 15 N values of samples from the 3 sample locations in each habitat (see Table 1 in the main article)
Over the last decade, hatchery production of mud crabs has become technically and economically mo... more Over the last decade, hatchery production of mud crabs has become technically and economically more feasible, enabling evaluation of the potential effectiveness of hatchery release in fisheries enhancement. The high growth rates and limited movement of ...
Ranching, stock enhancement and restocking are management approaches involving the release of wil... more Ranching, stock enhancement and restocking are management approaches involving the release of wild or hatchery-bred organisms to enhance, conserve or restore fisheries. The present study, conducted from April 2002 to November 2005, evaluated the effectiveness of releasing wild and hatchery-reared (HR) mud crabs in the mangroves of Ibajay, Aklan, Philippines where preliminary studies demonstrated declining fishery yields, abundance and size of crabs. Comparison of survival and growth of wild-released and HR Scylla olivacea and HR Scylla serrata demonstrated the effect of nursery conditioning, size-at-release and species differences. Overall yield and catch per unit effort (CPUE) increased by 46% after stock enhancement trials. Recapture rates of released crabs were highest in wild-released S. olivacea and in crabs measuring 65.0–69.9 mm carapace width (CW) and lowest in non-conditioned HR S. serrata. Growth rates were highest for conditioned HR S. olivacea and lowest for conditioned HR S. serrata (11.7 and 3.7 mm month–1 respectively). Fishing mortality was highest for S. olivacea, whereas natural mortality was greater for S. serrata. Conditioning hatchery-bred animals before release is also important in obtaining higher survival. S. olivacea was the more appropriate of the two species for release in mangrove habitats inundated with low-salinity water. However, there is a need for site-specific studies to evaluate the effectiveness of releases.
Brackishwater pond culture has been a major factor in mangrove loss in Southeast Asia, hence, the... more Brackishwater pond culture has been a major factor in mangrove loss in Southeast Asia, hence, the need to develop environment-friendly technologies such as mud crab Scylla (Portunidae) culture in mangrove pens exists. This study evaluated the e¡ects of mud crab netpen systems in central Philippines on mangrove macro£ora, and the replacement of dietary ¢sh with low-cost pellets.Wild or hatchery-sourced Scylla olivacea and Scylla serrata were stocked at 0.50 .8 m À 2 in 167^200 m 2 nylon netpens (2.3 cm stretched mesh) in Avicennia-dominated mangrove habitats. The feeding treatments were: (A) Zarraga: (1) no feeding (natural productivity), (2) no feeding for 1 month1supplementary feeding, (3) ¢sh biomass and (4) low-cost pellets, and (B) Batan: (1) ¢sh biomass and (2) pellets1¢sh biomass. Feeds were given ad libitum twice daily. Growth and survival rates of S. olivacea in Zarraga pens were not signi¢cantly different among treatments, although crabs fed ¢sh biomass had the highest survival, body weight and production. Similarly, growth and survival of S. serrata were not signi¢cantly di¡erent between the Batan treatments. Economic analysis of the latter gave a 38.5% return on investment (ROI) and 2.6 years payback period (PP) for pellets1¢sh biomass treatment compared with 27.5% ROI and 3.6 years PP for ¢sh alone. Sensitivity analysis showed an improved economic performance of the pellets1¢sh biomass treatment by increasing the survival rate. Evaluation of mangrove community structure showed that crab culture reduced species diversity, numbers and biomass of seedlings and saplings, but not of mangrove trees. Therefore, mud crab pen culture is recommended for mangrove sites with mature trees, but not seedlings and saplings, and low-cost pellets can reduce dependence on ¢sh biomass.
Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively ... more Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively fished throughout their range in the Indo-West Pacific. Despite this high level of exploitation very little is known about the population dynamics of any of the Scylla species. The present study concentrated on an exploited population of Scylla paramamosain in a natural estuarine mangrove on Can Coc Island in the mouth of the Hau River, Mekong Delta, Vietnam. A total of 6,114 juvenile crabs captured on the seaward mangrove fringe were internally tagged by injection of coded microwire tags and released over a period of 29 days. Recaptures were monitored over the following 144 days. There was little migratory movement within the estuary; of 285 recaptured crabs, 93% were recovered within the island mangrove study area and only two individuals were recovered from mangroves lining the opposite mainland riverbanks. A von Bertalanffy growth function was fitted to growth increment data from recaptured crabs, with L max = 150 mm to derive a growth constant, k = 2.39 year-1. The theoretical age at which carapace width is zero (t 0) was derived from known size at recruitment at instar 1, giving a value of-0.0095 years. Previous studies of the same population have shown that female S. paramamosain reach maturity at a mean size of 102 mm carapace width. The present study indicates that they attain this size at around 160 days from first settlement in the mangrove fringe. Abundance of juvenile crabs in the study area was estimated by the Petersen method as 1,101,500 (95% CI 4,17,300-1,785,800, representing 1,102 crabs ha-1 of mangrove. Estimation of mortality from tag returns and from the age-catch curves during a period of constant recruitment were comparable (Z = 1.11 and 1.04 month-1 , respectively). Fishing only accounted for 14% of total mortality, suggesting that at the time exploitation was not at a critical level despite the apparent high level of fishing activity. Communicated by A. Atkinson, Cambridge.
Offspring size variation in relation to maternal size and season is characteristic of a range of ... more Offspring size variation in relation to maternal size and season is characteristic of a range of species living in seasonal environments. Little is known about the proximate mechanisms explaining the links between maternally driven variation in offspring phenotypes, for instance when mothers have different diets depending on their size or the season. Here, we use stable isotopes techniques to quantify size dependent and seasonal variations in diet in mothers of shrimp Palaemon serratus and explore possible links between maternal diet and phenotype of embryos and freshly hatched larvae. We found that larger females, which occur more frequently in winter, produce larvae with higher carbon and nitrogen content as well as higher percent carbon, than smaller mothers collected in winter. In addition, isotopic composition suggest that larger mothers collected in winter, were feeding at a higher trophic level, or on an enriched prey pool compared with smaller mothers collected in summer. Ov...
Journal of the Korean Society For Marine Environment Energy, 2010
The paper describes the objectives of Yellow Sea Large Marine Ecosystem (YSLME) project, focusing... more The paper describes the objectives of Yellow Sea Large Marine Ecosystem (YSLME) project, focusing on procedural and practical aspects. YSLME is a highly productive sea yet possibly one of the most impacted large marine ecosystems, in terms of anthropogenic stressors, due the enormous coastal population. The aim of the YSLME project is the reduction of ecosystem stress through identification of the environmental problems in the Transboundary Diagnostic Analysis (TDA) that are then addressed in the Strategic Action Programme (SAP). One of the major problems found to be affecting biological diversity is habitat modification through wetland reclamation, conversion and degradation. Since the early 1900's more than 40% of intertidal wetlands have been reclaimed in Korea, and 60% of Chinese coastal wetlands have been converted or reclaimed. Damaging fishing practices, pollution and coastal eutrophication have further degraded the coastal environment reducing the biological diversity. To combat this loss, the YSLME project has mounted a public awareness campaign to raise environmental consciousness targeted at all different levels of society, from politicians at parliamentary workshops, local government officer training events, scientific conferences and involvement of scientists in the project research and reporting, to university and high school students in our visiting internship programmes and environmental †
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