First thorough assessment of de novo oocyte recruitment in a teleost serial spawner, the Northeast Atlantic mackerel (Scomber scombrus) case

The understanding of teleost fecundity type (determinate or indeterminate) is essential when deciding which egg production method should be applied to ultimately estimate spawning stock biomass. The fecundity type is, however, unknown or controversial for several commercial stocks, including the Northeast Atlantic mackerel (Scomber scombrus). Aiming at solving this problem, we applied state-of-the-art laboratory methods to document the mackerel fecundity type, including any de novo oocyte recruitment during spawning. Initially, active mackerel spawning females were precisely classified according to their spawning status. The number and size of all phasei-specific oocytes (12 phases), with a special attention to previtellogenic oocytes phases (PVO [PVO2 to PVO4a–c]), were also thoroughly investigated. Examinations of relative fecundity (RFi) clarified that the latest phase of PVOs (PVO4c) are de novo recruited to the cortical alveoli–vitellogenic pool during the spawning period, resulting in a dome-shaped seasonal pattern in RFi. Hence, we unequivocally classify mackerel as a true indeterminate spawner. As PVO4c oocytes were currently identified around 230 µm, mackerel fecundity counts should rather use this diameter as the lower threshold instead of historically 185 µm. Any use of a too low threshold value in this context will inevitably lead to an overestimation of RFi and thereby underestimated spawning stock biomass.

Environmental drivers of the abundance and distribution of forage fishes on the Northeast US shelf, with a particular emphasis on northern sand lance

Small pelagic fishes, also termed forage fishes, represent a critical link between secondary production and myriad top predators in marine ecosystems, including the Northeast US shelf. In this dissertation, I analyze the drivers of forage fish distribution throughout the Northeast US shelf and the drivers of the abundance of the ecologically important northern sand lance. Chapter 2 examines the basic ecology of northern sand lance and uses these insights to identify mechanistic drivers of their abundance. I then explore different scenarios of these drivers to project sand lance abundance through the end of the 21st century, which appears precarious for adult sand lance unless current trajectories change. Chapter 3 analyzes the environmental drivers of the distribution of the six dominant, offshore forage fish species (northern sand lance, Atlantic herring, alewife, blueback herring, Atlantic mackerel, and Atlantic butterfish) on the Northeast US shelf to elucidate the role of environmental covariates in shelf occupancy by these taxa. The results of this chapter indicate shelf occupancy of butterfish and Atlantic mackerel are increasing through time while occupancy of sand lance is decreasing with time. The occurrence of most of these species is also moving deeper and northward with time. Chapter 4 assesses the source-sink dynamics of three sand lance hotspots through Lagrangian particle tracking models simulating larval sand lance transport. Connectivity varies among these hotspots with Georges Bank and Stellwagen Bank having notable retention while the Great South Channel relies on larvae from other hotspots. Retention on Stellwagen Bank and Georges Bank are linked to strong wind events during the larval period of sand lance. Collectively, this dissertation improves our understanding of the dynamics driving variability in the Northeast US shelf forage fish complex, particularly for northern sand lance.

Skilful decadal-scale prediction of fish habitat and distribution shifts

Many fish and marine organisms are responding to our planet's changing climate by shifting their distribution (i.e. where they are found). Such shifts can drive conflicts at the international scale and are highly problematic for the communities and businesses that depend on these living marine resources for income and nutrition. Advances in climate prediction mean that in some regions the state of the ocean, and thereby the drivers of these shifts, can be skilfully forecast up to a decade ahead. However, the potential for these forecasts to benefit ocean-dependent communities has yet to be realised. Here we show for the first time that marine climate predictions can be used to generate decadal-scale forecasts of shifts in the habitat and distribution of marine fish species, as exemplified by Atlantic mackerel, bluefin tuna and blue whiting. We show statistically significant forecast skill of individual years that outperform both persistence and climatological baseline forecasts for lead times of 3-10 years: multi-year averages perform even better, yielding correlation coefficients in excess of 0.90 in some cases. We also show that the habitat shifts underling recent conflicts over Atlantic mackerel fishing rights could have been foreseen on similar timescales. Our results show that climate predictions can be translated into information directly relevant to stakeholders and we anticipate that this tool will be critical in foreseeing, adapting to and coping with the challenges of a changing and variable future climate, particularly in the most ocean-dependent nations and communities.

An investigation of green tea’s effect on mackerel (Scomber Scombrus)’s protein structure during frozen storage by FT-Raman spectroscopy

FT-Raman spectroscopy (FT-RS) was used to investigate green tea’s potential protective effect as an antioxidant during frozen storage of Atlantic mackerel (Scomber scombrus). Atlantic mackerel was stored for more than 26 weeks at −10°C or –80°C (control), with or without green tea (GT). Raman analysis showed substantial changes in protein structure due to frozen storage, especially at the higher storage temperature (−10°C), compared with the findings at −80°C or −10°C with instant GT, indicated by a decrease in the tyrosine doublet ratio, a-helix content. O-H stretching band intensity, along with an increase in tryptophan band intensity and β-sheet structure. GT as an antioxidant at a concentration of ~250 ppm can protect the structure of fish proteins for a limited storage period. However, for optimal freshness, fish should be stored at very low temperatures.

Technology Development of Immediately Fished Cuttings for Restaurants

The topicality. The current state of nutrition of Ukraine population is analyzed in the article, draws conclusions about the possible improvement of the situation by creating products from fish raw materials with the addition of functional food ingredients of plant origin, which will have improved organoleptic characteristics and increased energy and nutritional value, as well as recommended as a functional product in the diet of certain categories of the population. Purpose and methods. The purpose of the study is to substantiate the recipe of a new type of fish semi-finished products “Zrazy fish slices chopped with poppy and sesame seeds” with enrichment with their functional ingredients. The object of research is the technology of the semi-finished product “Zrazy fish cut with poppy and sesame seeds”. The subject of the study are semi-finished products “Zrazy fish slices”, semi-finished products “Zrazy fish slices with poppy seeds and sesame seeds”, Atlantic mackerel fillets (DSTU 4378: 2006), sesame seeds (DSTU 7012: 2009) and poppy seeds (DSTU 7696: 2015). Research methods: the research was based on methods of theoretical generalization, comparative analysis, and calculation, organoleptic. Results. The results of theoretical and experimental research of creation of technology of fish semi-finished product “Zrazy fish cut with poppy and sesame seeds” of functional purpose have been shown. The chemical composition of the main raw material of the dish – Atlantic mackerel has been analyzed and its advantages in the recipe composition have been proved. Possibility of using poppy seeds and sesame seeds as functional ingredients in the dish has been confirmed. The organoleptic parameters of the dish were studied and the optimal ratio of poppy seeds and sesame seeds in breadcrumbs has been determined. The nutritional, energy value and vitamin-mineral composition of the dish “Fish slices chopped with poppy and sesame seeds” have been calculated. Conclusions and discussions. The traditional recipe of the dish “Zrazy fish cut” has been analyzed. The expediency of modification of the traditional recipe due to the complete replacement of the main fish raw material with Atlantic mackerel fillet and the functional ingredients introduction of plant origin, namely poppy seeds and sesame seeds in breadcrumbs zrazy has been proved. The optimal content of poppy seeds and sesame seeds has been determined in the recipe of the dish “Fish cut with poppy seeds and sesame seeds”, which is 1.2% of poppy seeds and 0.6% of sesame seeds in breadcrumbs. It has been found that the variant of the recipe № 3 dishes “Zrazy fish slices cut with poppy and sesame seeds” has the best organoleptic quality indicators: harmonious taste properties, and due to the introduction of breading poppy and sesame seeds acquire an attractive and original appearance. It has been proved that the introduction of Atlantic mackerel fish fillets, poppy seeds and sesame seeds into the recipe composition allows to significantly increase the content of fats (5 times chopped fish with poppy seeds and sesame seeds) in fats (5 times), unsaturated fatty acids (4.5 times) , PUFA (6.9 times). The content of such minerals as calcium, magnesium, iron, and vitamins B2, B3, B6, PP, K, D in the dish increased by more than 50%. The latest recipe “Fish cut with poppy and sesame seeds” ensures the absorption of calcium in full due to the presence in its chemical composition of the optimal ratio of Ca: P: Mg = 1: 1,48: 0,5. The energy value of the dish has increased almost 1.5 times. The degree of daily nutrient requirements for men of the III working age group aged 30 to 39 years of the dish “Fish cut with poppy and sesame seeds” in such as dietary fiber (13.05%), PUFA (36.6%), calcium (12.99%), magnesium (18.88%), phosphorus (19.23%), vitamin D (258.4%).