Fish Spawning Grounds Research Articles

Long-term stability in modelled zooplankton influx could uphold major fish spawning grounds on the Norwegian continental shelf

Early life stages of fish spawned on the Norwegian continental shelf have long been suggested to depend on eggs and nauplii from the crustacean zooplankton Calanus finmarchicus for survival. Calanus finmarchicus overwinters in the deep basins of the Norwegian Sea, and gravid females must be advected onto the shelf prior to spawning if eggs and nauplii larvae are to serve as food for fish larvae. In this study, cross-shelf advection of C. finmarchicus is simulated over 52 years (1960–2011) using a numerical ocean model coupled with an individual-based model. The results suggest that cross-shelf transport of C. finmarchicus is surprisingly stable across years and that transport is particularly concentrated immediately upstream of the two major spawning areas for the Northeast Arctic cod (Gadus morhua) and the Norwegian spring-spawning herring (Clupea harengus), namely Lofoten and Møre, respectively. Two large topographical features, the Træna Trough and the Norwegian Trench, appear to be funnelling C. finmarchicus onto the shelf in these two areas. This could suggest that the fish spawning grounds outside Møre and Lofoten are, in part, maintained owing to stable interannual food supply in spring.

The potential of Indonesian mangrove forests for global climate change mitigation

Indonesian mangrove carbon stocks are estimated to be 1,083 ± 378 MgC ha−1. In the past three decades Indonesia has lost 40% of its 2.9 Mha of mangroves; this is estimated to have resulted in annual CO2-equivalent emissions of 0.07–0.21 Pg. Mangroves provide a wide range of ecosystem services, including nutrient cycling, soil formation, wood production, fish spawning grounds, ecotourism and carbon (C) storage1. High rates of tree and plant growth, coupled with anaerobic, water-logged soils that slow decomposition, result in large long-term C storage. Given their global significance as large sinks of C, preventing mangrove loss would be an effective climate change adaptation and mitigation strategy. It has been reported that C stocks in the Indo-Pacific region contain on average 1,023 MgC ha−1 (ref. 2). Here, we estimate that Indonesian mangrove C stocks are 1,083 ± 378 MgC ha−1. Scaled up to the country-level mangrove extent of 2.9 Mha (ref. 3), Indonesia’s mangroves contained on average 3.14 PgC. In three decades Indonesia has lost 40% of its mangroves4, mainly as a result of aquaculture development5. This has resulted in annual emissions of 0.07–0.21 Pg CO2e. Annual mangrove deforestation in Indonesia is only 6% of its total forest loss6; however, if this were halted, total emissions would be reduced by an amount equal to 10–31% of estimated annual emissions from land-use sectors at present. Conservation of carbon-rich mangroves in the Indonesian archipelago should be a high-priority component of strategies to mitigate climate change.

Fish assemblage structure on sandy beaches with different anthropogenic influences and proximity of spawning grounds

AbstractFish assemblages in an insular (preserved) and a continental (disturbed) sandy beach were compared to assess any changes that could be attributed to anthropogenic influences and/or the proximity of the fish spawning grounds. We expected that the closer geographical position to the spawning grounds and the small amount of anthropogenic disturbance on the insular beach would be likely to provide more suitable conditions for early fish development compared with the continental beach. A total of 192 samples (96 in each beach) were taken, yielding 68 fish species, mostly young‐of‐the‐year. Fish assemblage structure differed significantly between the two beaches. Moreover, the insular beach had higher number of species, number of individuals and biomass compared with the continental beach. The commercially important Clupeiformes Harengula clupeola, Anchoa tricolor and Anchoa januaria, Perciformes Micropogonias furnieri and Mugiliformes Mugil liza were typical species on the insular beach, partitioning the seasonal use of the beach. On the other hand, a few abundant non‐commercial species, mainly the Atheriniformes Atherinella brasiliensis and the Perciformes Eucinostomus argenteus and Diapterus rhombeus, occurred all year round at the continental beach. The high fish richness and abundance and the more conspicuous species turnover across seasons on the insular beach are probable indications of more complex and dynamic organization of the communities favored by better geographical position and less anthropogenic disturbance in the area.

Soil Erosion in Britain: Updating the Record

Concern about soil erosion on arable land in Britain dates back at least 40 years. Monitoring schemes and case studies have subsequently identified the areas at risk, the rates and frequencies and the major factors responsible for erosion. Initial concern focused on impacts on the farm and therefore on food production. Latterly the emphasis has shifted to off-farm impacts particularly reservoir sedimentation, muddy flooding of properties and the ecological damage to watercourses due to nutrient enrichment, pesticides and damage to fish spawning grounds from fine-sediment inputs. The shift has therefore been to concerns about a healthy and sustainable environment which includes soils. Government agencies, the water companies and the farming industry have lagged behind scientific studies in recognising and addressing erosion problems. Attempts at mitigation are now largely driven by the need to comply with the EU Water Framework Directive whereby watercourses must reach “good status” by 2015. Future changes in land use and climate will offer further challenges in terms of effective monitoring and compliance.

Integrating molecular identification of pelagic eggs with geostatistical mapping to improve the delineation of North Sea fish spawning grounds

Maps of the spawning grounds of commercially important fishes are necessary when assessing the level of connectivity between life stages of fishes and for identifying ecologically valuable marine areas. A first step toward mapping the spawning grounds is a reliable and rapid species identification of pelagic fish eggs to assess the spatio-temporal distribution of spawning aggregations. As many species have similar egg sizes and morphology, the molecular validation of visually identified eggs is often essential for the use of such data in fisheries management. In the present study, we developed a rapid 16S rRNA PCR-restriction fragment length polymorphism (RFLP) assay to distinguish between formalin-fixed fish eggs of dab Limanda limanda, flounder Platichthys flesus and pout Trisopterus spp., which were collected during the 2008 International Bottom Trawl Survey in the Eastern English Channel and southern North Sea. A comparison of the rapid 16S rRNA PCR-RFLP method with initial visual identification revealed 93% of correct identifications for dab, 90% for pout, but only 64% for flounder, representing an overall error rate of 17%. Visual misidentification occurred mainly between dab and flounder and between flounder and pout. Egg abundance and the relative proportions of each species were subsequently analysed geostatistically. Molecular identifications were incorporated to obtain corrected interpolated distribution maps, taking into account the results from molecular identifications as a correction factor. This highlighted the distinct spawning grounds for the 3 studied taxa and facilitated the identification of regions of high conservation value for these species.

Changes of biological communities in the Eastern Gulf of Finland during the last century

Changes in biological diversity of the Neva Estuary (eastern Gulf of Finland), which is one of the largest Baltic estuaries, were assessed by means of BSRP SGEH priority indicators. They include macrophytobenthos, macrozoobenthos, alien species, ichthyofauna, avifauna, mammals and a portion of the territory covered by the protected areas. The most prominent biodiversity changes were observed in the upper freshwater Neva Bay, and moderate changes, in the lower brackish part of the estuary. Eutrophication, alien species and dredging activities are the major threats to biodiversity of the estuary. At present, alien species contribute about 8 per cent of species richness, however, 60-90 per cent of the biomass of bottom animals. Filamentous algae blooms affect biodiversity of zoobenthos in the shallow coastal zone. The climate-mediated fluctuations in near-bottom oxygen conditions are responsible for deterioration of zoobenthos in the open waters of the estuary. The decline of the benthic aboriginal crustaceans led to impairment of food conditions for fish and to a sharp reduction of their populations, which, in turn, was partly responsible for the population decline of ringed seals. Milder winters have also contributed to the decline in the numbers of this species. Dredging activities related to construction of new lands and ports are the main factor affecting fish, submerged macrophytes and waterfowl in Neva Bay. A considerable part of fish spawning grounds and waterfowl habitats in Neva Bay has been lost during the last decades. The long-term measures for conservation and improving of biodiversity should take into account periodicity of climatic changes and planned development of the region.

Dispersal of Contaminants from Municipal Discharges as Evidenced from Sedimentary Records in a Great Lakes Coastal Wetland, Cootes Paradise, Ontario

Cootes Paradise is a coastal wetland, at the western end of Lake Ontario. The marsh, which is an important spawning ground for fish and a crucial habitat for other species, has been considerably degraded by excessive contaminant inputs from wastewater treatment plants (WTPs), marsh tributaries, and Combined Sewer Overflows (CSOs). These discharges are not only major sources of nutrients (e.g., phosphorus) to the marsh, but are also the main contributors of pharmaceuticals, hormones, and other wastewater contaminants. Studies have shown that many of these compounds are toxic and have estrogenic effects on organisms living in the vicinity of these sources. This study investigates dispersal of contaminants from nearby point sources, as determined from sediment contamination, both spatially and stratigraphically. This was accomplished by establishing the trends and utilizing the relationships between limiting nutrient phosphorus, estrogenic alkylphenols, and faecal sterols, specifically, coprostanol. High levels of phosphorus (1,655–1,987 mg TP kg −1) and alkylphenolics (2.51–4.89 mg kg −1) were measured in sediments near the discharge outlets. Statistical analysis revealed a close relationship between investigated pollutants and the molecular marker coprostanol, and provides evidence of significant sediment contamination near the discharge points, suggesting deposition of most contaminants within a short distance from the points of entry and limited dispersal of pollutants within the wetland. The stratigraphic distribution of pollutants, which reflects the historical trends, reveals major spikes in pollutant concentrations near point sources that could be attributed to episodic events of major significance and shows a long persistence of the investigated contaminants in sedimentary environments.

Occurrence of alkylphenolic substances in a Great Lakes coastal marsh, Cootes Paradise, ON, Canada

Occurrence and fate of alkylphenols (APs), known endocrine disruptors, were investigated in a Great Lakes coastal wetland, Cootes Paradise, ON. The wetland, which receives discharges from a Wastewater Treatment Plant (WTP) and several Combined Sewer Overflows (CSOs), is an important spawning ground for fish and crucial habitat for other fauna. Elevated concentrations of nonylphenol ethoxylates (NPEs) and their degradation product nonylphenol (NP) were found in water and sediment samples near the sources. Since transfer of APs through the food chain is of concern, we compared their concentrations in invertebrates from clean and contaminated sites. The results reveal transfer of alkylphenolics from sediments to biota and their accumulation in the invertebrate tissue, particularly the highly hydrophobic 4-NP, whose concentrations ranged from 1.9 to 6.3 μg g -1. To our knowledge, this is the first study to evaluate AP concentrations in tissue of benthic invertebrates under real environmental conditions.

A STUDY ON COASTAL STRUCTURES AS FISH SPAWNING GROUNDS LIGHT AND FLOWS AROUND SPAWNING GROUNDS OF SANDFISH

In recent years, spawning of sandfish was observed in gulfweeds adhering to a breakwater in a sandy beach area of the Tomakomai East Port. This suggested that the breakwater served as a reef for sandfish to spawn on.This study focused on light and flows around a spawning ground of sandfish, for the purpose of adding a function as fish spawning grounds to breakwaters and other coastal structures. The study was based on the results offield surveys conducted in the Tomakomai East Port, where spawning on a breakwater had been observed, and in the Nemuro sea area, which is known as a natural spawning ground.As a result, it was found that gulfweeds were distributed mainly at depths where light attenuationfactors were over the approximate range of 0.05 to 0.09, although distribution depths differed between the Tomakomai East Port and the Nemuro sea area. Also, in spawning grounds of sandfish, the flow velocity at the time of adhesion of gulfweed embryos was considered to be of higher significance than that during spawning.

Thiobencarb-induced embryotoxicity in medaka ( Oryzias latipes): stage-specific toxicity and the protective role of chorion

Thiobencarb ( S-(4-chlorobenzyl)- N, N-diethyl thiol carbamate) has been one of the herbicides previously associated with fish kills in agricultural drains near the Sacramento/San Joaquin rivers and their Delta. This area is an important spawning ground for fish, and thus there are concerns over possible toxic effects on early life stages of fishes. To define targets of thiobencarb embryotoxicity and to determine the degree of protection afforded by the chorion, medaka ( Oryzias latipes) embryos were exposed under static nonrenewal conditions. Responses to exposures initiated at blastula or at initiation of heart beat (stages 10 and 23, respectively) were assessed. In addition, enzymatically dechorionated embryos (stage 13, gastrula) were exposed and compared to responses in embryos with intact chorions. Embryos were observed daily for development and for gross abnormalities including: bradycardia, pericardial edema, hemostasis, poor yolk resorption, cephalic and spinal deformities, and abnormal hatching. A subset was also evaluated for histologic alterations. Based on gross abnormalities, the concentration of thiobencarb affecting 50% (EC 50) of embryos exposed at blastula was 3.6 mg/l, while the putative no observable effect concentration (NOEC) was 1.0 mg/l. For embryos exposed at onset of heart beat (stage 23), these values were 4.1 and 2.5 mg/l, respectively. Dechorionated embryos tended to be more sensitive than their chorionated cohorts (LC 50=2.5 vs. 1.0 mg/l). Liver histologic alterations were seen in chorionated embryos at EC 50 levels and higher. Stage-specific toxicity was evident; nevertheless, the EC 50 and NOEC values for embryos treated at stage 10 and stage 23 were similar.

Research on a method of the breeding of seaweed beds on coastal structures

In the ocean, seaweed has a major influence on marine resources, by providing spawning grounds for fish, breeding grounds for fry and feed for seaweed-eating creatures. Seaweed itself is also a marine food resource. It also plays an important role in conservation of the global environment as it settles carbon dioxide, which is a cause of global warming, by photosynthesis.In the future development of coastal areas, taking into consideration the breeding of seaweed on breakwaters and other coastal structures will be as important as conserving existing seaweed beds.The authors have found two ways for artificial formation of seaweed beds. One is the rear step method, which is a structural improvement to place flat beds behind the sloping breakwater to facilitate the breeding of seaweed. The other is a method to help seaweed adhere by improving materials and structure surface forms.It was found from the research that sloping breakwater with rear step were very effective for the formation of seaweed communities and there was more seaweed on structures with an uneven surface.

Device for finely resolved sampling of littoral lake regions: Design and operation

AbstractAlthough littoral regions in northern lakes may sustain fish spawning grounds, little is known of the temporal or spatial aspects of their thermal and chemical regimes. This shortcoming is due in part to the difficulty in properly sampling these regions throughout the year with adequate spatial resolution. This problem is especially critical in lakes affected by episodic acidification during the spring snowmelt, a period of substantial importance to fisheries recruitment. A device was constructed to alleviate the problems associated with conventional water quality sampling of littoral regions. Constructed of thick walled polyvinyl chloride and permanently installed in the nearshore regions of an Adirondack lake, the episodic event sampler (EES) provided finely resolved (0.25 m) temperature and water chemistry data during the spring snowmelt period (February to May) of 1989. Although the construction and installation of the sampler represented a significant investment in labour and materials, this was offset by the high quality of the data collected. As the samplers were relatively undamaged by freeze‐thaw activity, it is expected that they will continue to provide excellent information for several years.

Rivers of Sawdust: The Battle Over Industrial Pollution in Canada, 1865-1903

This article deals with the debate over the pollution of waterways in eastern Canada from 1866 to 1903. Water-powered sawmills, producing lumber largely for export to the United States, poured vast amounts of sawdust and mill waste into major river systems, fouling fish spawning grounds, choking navigable channels and leading to instances of spontaneous explosion. From 1866 onward, criticism of these abuses by the lumber industry grew. The controversy over sawdust pollution focussed on the Ottawa River, where influential lumbermen carried on their operations in sight of Parliament Hill. The battle to end sawdust dumping on the Ottawa — the practice was not stopped until 1903 — led to an important victory for early environmentalists in Victorian Canada.

Biomass and Salinity Tolerance of Shoalgrass and Manateegrass in Lower Laguna Madre, Texas

Three different shoalgrass (Diplanthera wrightii) stands and a manateegrass (Syringodium filiforme) community in Lower Laguna Madre, Texas, were sampled for their plant biomass. The winter standing crop of all (wet) shoalgrass herbage and roots is estimated to be 317,345 tons, a yield of 4,656 lb/acre. The standing crop of (wet) manateegrass is estimated to be 48,214 tons, a yield of 5,795 lb/acre. Shoalgrass exhibits a seasonal abundance, the smallest standing crop occurring in late winter and spring. Manateegrass is not seasonal in abundance. Shoalgrass sprigs planted in culture vessels lived in salinities ranging from 9.0 to 52.5 parts per thousand (ppt), but died in salinities of 3.5 ppt, and 70.0 ppt, or more. Manateegrass rhizomes planted in culture vessels survived best in a sa- linity of 35.0 ppt, while those planted in a vessel containing 52.5 ppt died. Shoalgrass is an important food of waterfowl wintering in Lower Laguna Madre, and provides spawning and nursery grounds for fish and shrimp. Manateegrass appears to be of minimal value to fish and waterfowl. If the usual sa- linity of Laguna Madre is permanently decreased by construction of fish passes from the Gulf of Mexico, or by drainages from river diversion projects, the shoalgrass biomass is likely to be reduced and the production promoted of manateegrass or other marine spermatophytes intolerant of hypersaline water. In terms of fish and wildlife, the Lower Laguna Madre is probably the most im- portant bay along the Texas coast. The lagoon has become the leading producer of important bay fishes with the general de- cline of commercial production in other bays (Breuer 1962:153). The Lower La- guna Madre also winters about one-half million waterfowl annually, including ap- proximately 78 percent of the existing red- head duck (Aythya americana) population (Weller 1964:64). One reason for the exceptional abundance of fish and waterfowl in Lower Laguna Madre is dense stands of shoalgrass, a sub- mergent marine spermatophyte which pro- vides cover and spawning grounds for fish and shrimp. Shoalgrass also is the chief plant food of most ducks wintering in South Texas bays (Singleton 1953:46). Manatee- grass, another submergent spermatophyte, extends in a near homogeneous stand over a large area of the southern part of Lower 1 This paper is a contribution from the Pittman-