Thirty years of change and the future of Alaskan fisheries: Shifts in fishing participation and diversification in response to environmental,regulatory and economic pressures

Heterogeneity in human responses and decision‐making can contribute to the resilience of social–ecological systems in the face of environmental, political and economic pressures. In fishery systems worldwide, the ability of harvesters to maintain a diverse portfolio of fishing strategies is important for building adaptive capacity. We used a case‐study approach to examine the complexity of factors that inhibit or promote diversification in fisheries of Alaska, one of the major fishing regions of the world. Through a combination of harvest records and literature review, we explored shifts in participation and portfolio diversity in Alaskan fisheries over three decades. The four case‐studies examined the responses of fishers, fleets and communities to multiple, intersecting pressures, including biological declines, market and price dynamics, fishery privatization and the 1989 Exxon Valdez oil spill. These cases illustrate how stressors acting at multiple scales can encourage or constrain opportunities for diversification, and that these opportunities may be spread inequitably across participants. Overall, we found evidence for reduced participation and increasing specialization in Alaskan commercial fisheries. While numerous factors explain these trends, policies like individual quota systems and the increasing cost of entry into fisheries are forcing consolidation at local to regional scales. A portfolio approach to managing fisheries that reduces barriers to diversification and includes broad representation of resource users and communities in management may help to maintain opportunity and choice for fishers.     

Retrospective analysis of the influence of environmental drivers on commercial stocks and fishing opportunities in the Irish Sea

Irish Sea fisheries have undergone considerable change in recent years following the decline of commercially important finfish stocks and their slow response to management's recovery plans. In 2015, the fishing industry called for a holistic exploration into the impact of environmental change and food web effects to identify the drivers underpinning stock dynamics. In this study, we identify correlations between large‐scale climatic indicators, temperature, primary and secondary productivity, and fish recruitment in the Irish Sea and incorporate them into an Ecopath with Ecosim food web model co‐created by scientists and fishers. Negative correlations were found between the North Atlantic Oscillation winter index (NAOw) and large zooplankton abundance and between the Atlantic Multidecadal Oscillation (AMO) and the recruitment of cod (Gadus morhua) and whiting (Merlangius merlangus). Using correlation analyses to direct the addition of environmental drivers to the Irish Sea ecosystem model improved the models fit against observed biomass and catch data and revealed the indirect impacts of environmental change as mitigated through trophic interactions. Model simulations suggest that historic environmental change suppressed the overall production of commercial finfish, limiting opportunities for the fishing industry, whilst also dampening the rate of stock recovery despite marked reductions in fishing effort. These results suggest that failure to account for ecosystem information may lead to misconceived expectations and flawed fisheries management; therefore, there is a need to operationalize ecosystem information through management procedures to support fisheries advice.     

Shrimp (Litopenaeus vannamei) production and stable isotope dynamics in clear‐water recirculating aquaculture systems versus biofloc systems

Closed recirculating aquaculture systems (RAS) offer advantages over traditional culture methods including enhanced biosecurity, the possibility of indoor, inland culture of marine species year‐round and potential marketing opportunities for fresh, never‐frozen seafood. Questions still remain regarding what type of aquaculture system may be best suited for the closed‐system culture of marine shrimp. In this study, shrimp (Litopenaeus vannamei) were grown in clear‐water RAS and in biofloc‐based systems. Comparisons were made between the system types with respect to water quality, shrimp production and stable isotope dynamics used to determine the biofloc contribution to shrimp nutrition. Ammonia and nitrite concentrations were higher, and shrimp survival was lower in the biofloc systems. Although stable isotope levels indicated that biofloc material may have contributed 28% of the carbon and 59% of the nitrogen in shrimp tissues, this did not correspond with improved shrimp production. Overall, the water column microbial communities in biofloc systems may be more difficult to manage than clear‐water RAS which have external filters to control water quality. Biofloc does seem to offer some nutritional contributions, but exactly how to take advantage of that and ensure improved production remains unclear.     

Patterns and impacts of fish bycatch in a scallop dredge fishery

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The development ofRhizoctonia solani Kühn on the underground parts of the potato plant

Summary The development of the sclerotia (black scurf) ofRhizoctonia solani Kühn, on potato tubers is related to tuber maturity and the health of the root and stolon systems. Few sclerotia formed on tubers from untreated plants until the onset of plant senescence when, as the tubers matured and roots and stolons decayed, sclerotia developed both rapidly and extensively. Application of acid to haulms in early August led to an increase in black scurf on tubers, initially related to the increase in root and stolon infection, but especially after later harvests, to the degree of tuber maturity. Later in August, scurf increases were paralleled both by tuber changes and root and stolon infection. My mid-September, when acid application was to plants becoming senescent, there was little difference between patterns of infection found on treated and check plants.

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Zusammenfassung In diesem Artikel wird der Fortlauf der Infektion durchRhizoctonia solani Kühn an Wurzeln. Stolonen und Knollen beschrieben. Ferner wird der Einfluss der Krautvernichtung und des zeitlichen Abstandes zwischen ihr und der Ernte auf diese Infektion untersucht. Pflanzknollen der Sorte Majestic wurden am Kronenende direkt vor dem Auspflanzen mit vier Isolaten vonR. solani (aus Sklerotien von Kartoffelknollen) inokuliert. An den ausgelesenen Knollen war keine Pockenkrankheit sichtbar. Das Kraut wurde an einem von fünf Daten gespritzt resp, nicht gespritzt und die Pflanzen nachher in Intervallen geerntet (Tabelle 1). Wurzel- und Stolonenteile wurden gewaschen, dann auf Leitungswasseragar, das 50 mg Neomycin und Chloramphenicol proliter enthielt, gebracht und vor der Beurteilung auf Rhizoctoniabefall w?hrend 48 Stunden bei Zimmertemperatur bebrütet. Die Pflanzknollen wurden gem?ss Tabelle 2 auf Sklerotienbefall beurteilt. Zur Reifesch?tzung wurde jede Knolle der L?nge nach geschnitten und der Prozentsatz des Periderms notiert, das mit einer Pinzette entfernt werden konnte, wenn man am Kronenende begann. Die Kontrollpflanzen hatten bis Mitte September bei nur beschr?nkter lokaler Infektion durchR. solani (Abb. 1 und 2) relativ gesunde Untergrundsysteme. In den folgenden drei Wochen reiften die Knollenperiderme. Wurzeln und Stolonen wurden weitgehend vom Pilz besiedelt. Folglich ?nderte sich die N?hrstoffversorgung des Pilzes, eine Situation, von der man weiss, dass sie die Entwicklung zur Sklerotienbildung f?rdert. Mitte September widerspiegelt sich die ?nderung in der Ern?hrung in einem Ansteigen der Anzahl von Knollen mit Pocken und in deren Ausdehnung auf den Knollen (Abb. 3 und 4). Krautvernichtung mit S?ure Anfang August führte zu einer Zunahme der Pockenkrankheit, was anf?nglich auf eine Zunahme der Wurzel- und Stoloneninfektion, sp?ter aber auf den Grad der Knollenreife (Abb. 5) in Beziehung stand.: Sp?ter, im August, wurden die Krankheitszunahmen mit Knollen?nderungen wie mit Wurzel- und Stoloneninfektion gleichlaufend. Die S?ureanwendung Mitte September geschah an alternden Pflanzen und ?nderte das an Kontrollpflanzen beobachtete Infektionsbild wenig.

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Résumé Cet article décrit l'évolution de la contamination, parRhizoctonia solani Kühn, des racines, stolons et tubercules de pommes de terre, et examine l'influence du défanage et de l'intervalle défanagerécolté sur une telle contamination. Des tubercules de la variété Majestic n'étant pas visuellement porteurs de sclérotes ont été inoculés à la couronne, juste avant la plantation, avec 4 souches deR. solani provenant de sclérotes sur tubercules de pommes de terre. Les tiges ont été ou n'ont pas été défanées à 5 dates différentes et on a récolté ensuite les tubercules à intervalles réguliers (tableau 1). Les fragments de racines et de stolons ont été lavés, placés sur une gelose à l'eau du robinet, contenant 50 mg de néomycin et de chloramphénicol par litre, et mis à incuber 48 heures à température ambiante avant notation de l'infection parR. solani. La notation des sclérotes sur tuberculesfils a été effectuée comme cela est indiqué dans le tableau 2. Comme estimation de la ‘maturité’ chaque tubercule a été coupé selon l'axe longitudinal et on a noté le pourcentage de périderme, en partant de la couronne qui a pu être enlevé avec des pinces. Les plantes témoins ont eu leurs systémes souterrains relativement sains jusqu'à la mi-septembre avec des contaminations locales parR. solani, limitées (figures 1 & 2). Les trois semaines suivantes, la maturité des tubercules a augmenté et les racines et stolons ont été fortement contaminés par le champignon. Le support nutritionnel du champignon a donc été altéré, cet élément connu permet de stimuler la maturité des sclérotes en cours de formation. Vers la mi-septembre, des changements nutritionnels se sont soldés par une augmentation du nombre de tubercules porteurs de sclérotes et par l'extension de ces derniers (figures 3 & 4). Le défanage aux colorants nitrés début ao?t a entrainé une augmentation des sclérotes, qui s'était manifestée initialement par une augmentation de la contamination des racines et stolons, et plus tard au niveau du degré de maturité du tubercule (figure 5). Plus tardivement en ao?t, l'augmentation des sclérotes allait de paire avec le changement de tubercule et avec la contamination des racines et stolons. Vers la mi-septembre, le défanage sur des plantes proches de la senescence a eu un léger effet sur la contamination des plantes témoins.

     

Method for Determining Apparent Digestibility of Carbohydrate and Protein Sources for Artificial Diets for Juvenile Sea Cucumber,Australostichopus mollis

Effective nursery diets can greatly reduce the cost of producing juvenile sea cucumbers for release to aquaculture or restocking programs. However, methods for systematically testing the bioavailability of artificial diet ingredients for sea cucumbers are poorly developed, and consequently, there has been little research in this field. The current study presents methods developed to test the suitability of common carbohydrate and protein sources for inclusion in artificial diets for juvenile Australostichopus mollis. Apparent digestibility of carbohydrates was moderate and did not exceed 50% for any carbohydrates assayed. Wheat starch and carrageenans showed the highest digestibility amongst carbohydrates. Differences in apparent digestibility were not reflected in growth performance of juvenile A. mollis fed carbohydrate diets; overall growth performance was poor for all diets. Artificial protein sources consistently exhibited higher apparent digestibility, ranging from 75.1% for fish meal to 98.1% for casein. Low‐cost protein sources, like meat meal, show promise for future use in artificial diet formulation. However, delivering high protein content may reduce ingestion rates and thereby lower overall digestive efficiency in juveniles. Results show that artificial carbohydrate sources have some potential as diet constituents for juvenile sea cucumbers but are unsuitable as primary energy sources. Future testing of artificial carbohydrate sources for A. mollis may require predigestion to improve digestibility.     

Management practices to control premature senescence in Bt cotton

Commercial cultivation of Bt cotton produced higher boll load which led to stiff inter-original competition for photosynthates, resulting in early cessation of growth (premature senescence) due to more availability of sink and less sources. To overcome this problem, field experiment was conducted during 2011 and 2012 using five treatments of plant growth manipulation viz. no fruiting branch removal (F₁), removal of first fruiting branch (F₂), removal of first and second fruiting branch (F₃), removal of all squares from first fruiting branch (F₄), removal of all squares from first and second fruiting branches (F₅), and three potassium (K) application rates viz. 50 kg ha^?1 (K₁), 100 kg ha^?1 (K₂), and 150 kg ha^?1 (K₃). More nodes above white flower were recorded in F₅, followed by F₃, while minimum were recorded in F₁. Among potassium levels, maximum nodes above white flower were recorded in K₃ followed by K₂ and K₁ during both years of study. Plant height recorded at physiological cutout stage or at maturity stage showed that plants gained more height with removal of all squares from first tosecond fruiting branches with higher potassium dose. Leaf K increased with increasing applied potassium and also with square/branch removal. So early removal of squares/fruiting branches along with higher potassium dose helped in delaying canopy senescence in Bt cotton.     

Nutrient limitations to bacterial and fungal growth during cellulose decomposition in tropical forest soils

Nutrients constrain the soil carbon cycle in tropical forests, but we lack knowledge on how these constraints vary within the soil microbial community. Here, we used in situ fertilization in a montane tropical forest and in two lowland tropical forests on contrasting soil types to test the principal hypothesis that there are different nutrient constraints to different groups of microorganisms during the decomposition of cellulose. We also tested the hypotheses that decomposers shift from nitrogen to phosphorus constraints from montane to lowland forests, respectively, and are further constrained by potassium and sodium deficiency in the western Amazon. Cellulose and nutrients (nitrogen, phosphorus, potassium, sodium, and combined) were added to soils in situ, and microbial growth on cellulose (phospholipid fatty acids and ergosterol) and respiration were measured. Microbial growth on cellulose after single nutrient additions was highest following nitrogen addition for fungi, suggesting nitrogen as the primary limiting nutrient for cellulose decomposition. This was observed at all sites, with no clear shift in nutrient constraints to decomposition between lowland and montane sites. We also observed positive respiration and fungal growth responses to sodium and potassium addition at one of the lowland sites. However, when phosphorus was added, and especially when added in combination with other nutrients, bacterial growth was highest, suggesting that bacteria out-compete fungi for nitrogen where phosphorus is abundant. In summary, nitrogen constrains fungal growth and cellulose decomposition in both lowland and montane tropical forest soils, but additional nutrients may also be of critical importance in determining the balance between fungal and bacterial decomposition of cellulose.     

Improved Calibration for Estimating Soil Properties with a Multifunctional Heat Pulse Probe

A multifunctional heat pulse probe (MFHPP) can measure soil thermal and hydraulic properties. Though its successful implementation has been documented, previous studies have reported some limitations. One specific cause of the limitations is the absorption of the generated heat pulse within the probe itself, which creates error in the measurements. The objective of this study was to develop and evaluate a new calibration method to account for measurement error due to heat loss to the probe. A MFHPP was constructed and tested in six soil types using both a traditional method and the newly developed calibration method. The new calibration utilizes heat pulse response curves from real soils with thermal conductivities similar to that of the MFHPP rather than the traditional agar-stabilized water solution. This new approach significantly reduced average measurement errors from 9.1% to 2.4% for heat capacity and 13.5% to 4.5% for volumetric water content.     

Comparison of lipid content and Fatty Acid composition in the edible meat of wild and cultured freshwater and marine fish and shrimps from china

The lipid content and fatty acid composition in the edible meat of twenty-nine species of wild and cultured freshwater and marine fish and shrimps were investigated. Both the lipid content and fatty acid composition of the species were specified due to their unique food habits and trophic levels. Most of the marine fish demonstrated higher lipid content than the freshwater fish, whereas shrimps had the lowest lipid content. All the marine fish and shrimps had much higher total n-3 PUFA than n-6 PUFA, while most of the freshwater fish and shrimps demonstrated much lower total n-3 PUFA than n-6 PUFA. This may be the biggest difference in fatty acid composition between marine and freshwater species. The cultured freshwater fish demonstrated higher percentages of total PUFA, total n-3 PUFA, and EPA + DHA than the wild freshwater fish. Two freshwater fish, including bighead carp and silver carp, are comparable to the marine fish as sources of n-3 PUFA.