The Effect of Multiple Freeze–Thaw Cycles on the Microstructure and Quality of Trachurus murphyi

Temperature fluctuation in frozen food storage and distribution is the perpetual and core issue faced by the frozen food industry. Ice recrystallisation induced by temperature fluctuations under cold storage causes microstructural changes in fish products and irreversible damages to cells and tissues, which lower the frozen fish quality in the food chain. This study is intended to explore how repeated freezing–thawing affected the microstructure and quality of Trachurus murphyi during its frozen storage. The results showed the consistency between the increase in ice crystal diameter, volume, and porosity in frozen fish and the increase in centrifugal loss (from 22.4% to 25.69%), cooking loss (from 22.32% to 25.19%), conductivity (from 15.28 Ms/cm to 15.70 Ms/cm), TVB-N (from 16.32 mg N/100 g to 19.94 mg N/100 g), K-value (from 3.73% to 7.07%), and amino acid composition. The muscle structure change observed by Fourier-Transform Infrared spectroscopy (FT-IR) showed that the content of α-helix reduced from 59.05% to 51.83%, while the β-sheet fraction grew from 15.44% to 17.11%, β-turns increased from 5.45% to 7.58%, and random coil from 20.06% to 23.49%. Moreover, muscular structure exhibited varying degrees of deterioration with increasing cycles of freezing and thawing as shown by scanning electron microscopy (SEM). We studied the muscular morphology, which included the measurement of porosities (%) of pore that increased (from 1.4% to 4.3%) and pore distribution, by X-ray computed tomography (uCT). The cycles of the freeze–thaw resulted in structural changes, which seemed to be closely associated with ultimate quality of frozen fish products.

ICTIOPARASITOLOGÍA MARINA EN EL SISTEMA DE AFLORAMIENTO DE LA CORRIENTE DE HUMBOLDT: DESAFÍOS PARA LA REVISTA NEOTROPICAL HELMINTHOLOGY

El Sistema de Afloramiento de la Corriente de Humboldt, definido como “a Large Marine Ecosystem”, se extiende a lo largo de la Costa Occidental de América del Sur, desde la zona Centro Sur de Chile (app. 42°S) hasta el Norte del Perú (4°S). Es uno de los mayores sistemas de afloramiento del mundo y responsable por los extraordinariamente altos niveles de producción. Es considerado un sistema clase 1, altamente productivo (>300 g·C/m2-año). Los altos valores de producción primaria de este sistema soportan las más grandes pesquerías a nivel mundial (Alheit & Bernal, 1993). Alrededor del 18-20% de las capturas mundiales provienen de este sistema, específicamente de pelágicos pequeños como anchoveta (Engraulis ringens Jenyns, 1842), sardina (Sardinops sagax (Jenyns, 1842)) y jurel (Trachurus murphyi Nichols, 1920). De un sistema de estas características deberá esperarse una alta diversidad biológica.

ICTIOPARASITOLOGÍA MARINA EN EL SISTEMA DE AFLORAMIENTO DE LA CORRIENTE DE HUMBOLDT: DESAFÍOS PARA LA REVISTA NEOTROPICAL HELMINTHOLOGY

El Sistema de Afloramiento de la Corriente de Humboldt, definido como “a Large Marine Ecosystem”, se extiende a lo largo de la Costa Occidental de América del Sur, desde la zona Centro Sur de Chile (app. 42°S) hasta el Norte del Perú (4°S). Es uno de los mayores sistemas de afloramiento del mundo y responsable por los extraordinariamente altos niveles de producción. Es considerado un sistema clase 1, altamente productivo (>300 g·C/m2-año). Los altos valores de producción primaria de este sistema soportan las más grandes pesquerías a nivel mundial (Alheit & Bernal, 1993). Alrededor del 18-20% de las capturas mundiales provienen de este sistema, específicamente de pelágicos pequeños como anchoveta (Engraulis ringens Jenyns, 1842), sardina (Sardinops sagax (Jenyns, 1842)) y jurel (Trachurus murphyi Nichols, 1920). De un sistema de estas características deberá esperarse una alta diversidad biológica.

A first assessment of atresia in the Chilean jack mackerel Trachurus murphyi (Teleostei, Carangidae) from the South-eastern Pacific Ocean

The Chilean jack mackerel Trachurus murphyi support an important fishery in the South-eastern Pacific Ocean and has declined considerably over time. T. murphyi have asynchronous ovarian development with an oceanic spawning (September to January). Despite the economic importance of this resource critical issue such as characteristics and dynamics of atresia, which affect the reproductive output, are unknown. Females of T. murphyi caught in different spawning seasons were analysed to describe patterns of prevalence and intensity of atresia. General linear models (GLM) were performed by using prevalence and intensity atresia as response variables and gonadosomatic index, condition factor, sea surface temperature, postovulatory follicles and month/year as explanatory variables. The batch fecundity and relative fecundity were compared between females showing atresia, postovulatory follicles and non-atretic females. The stages of atresia identified were alpha, beta and gamma. The GLM showed that variations in the prevalence and intensity of atresia were explained for all variables, except condition factor for prevalence, and gonadosomatic index for intensity of atresia. According to our results, the dynamic of alpha and beta atresia could be considered a potential proxy for any disruption of spawning season. The batch fecundity and relative fecundity were lowest compared with other Trachurus spp. This is the first assessment comparing fecundity between atretic and not atretic females for this species.

Overlap of Pink-footed Shearwaters and central Chilean purse-seine fisheries: Implications for bycatch risk

Understanding susceptibility of seabirds to fisheries bycatch requires quantifying overlap of seabird at-sea habitat with fisheries’ distribution and effort. Pink-footed Shearwaters (Ardenna creatopus) are vulnerable seabirds that breed only in Chile. Recently, high rates of Pink-footed Shearwater bycatch (i.e. >1,500 observed mortalities 2015–2017) were documented by observers in central Chilean purse-seine fisheries. We present analysis of Pink-footed Shearwater at-sea movements and overlap with central Chilean purse-seine fleets targeting common sardine (Strangomera bentincki), Peruvian anchoveta (Engraulis ringens), and Chilean jack mackerel (Trachurus murphyi). To determine overlap during 2015–2017, we paired locations from 49 Pink-footed Shearwaters rearing nestlings at Isla Mocha, Chile, with locations and number of observed purse-seine sets in central Chile. Pink-footed Shearwaters typically visited waters ≤30 km offshore throughout central Chile. Foraging trip durations varied interannually, with longer trips in 2016, but all years revealed persistent foraging hotspots near Valdivia, the Gulf of Arauco, and Isla Mocha, Chile. Greatest overlap between Pink-footed Shearwaters and fisheries occurred with the sardine/anchoveta fleet near Valdivia (artisanal and industrial) and the Gulf of Arauco (artisanal); overlap with the jack mackerel fleet was minimal. Given Pink-footed Shearwater bycatch documented in these fisheries, this overlap may indicate risk of bycatch for these birds, although we did not directly quantify shearwater–fisheries interaction. Our results can inform further fishery monitoring efforts, as well as collaboration among scientists, managers, and fishers to identify, quantify, and reduce fisheries bycatch of Pink-footed Shearwaters within Chile and internationally.

Mineral Composition and Fatty Acid Profile of Smoked Horse Mackerel Trachurus Murphyi Using an Improved Fish Smoking Kiln

The purpose of this research was to determine the quality of mineral and fatty acid profile of imported horse mackerel Trachurus murphyi using the improved NIOMR fish smoking kiln. 20kg of frozen imported horse mackerel were obtained from Ijora frozen food market Lagos state, Nigeria. Samples were transported to the NIOMR Pilot plant for processing and commencement of chemical analysis. Results show that, the most abundant saturated fatty acid in the fish was Palmitic acid, with a value of 19.404%, while the most abundant monounsaturated fatty acid was Elaidic acid with a value of 12.63%. However, low values of polyunsaturated fatty acid was recorded in the fish species, and the most abundant polyunsaturated fatty acid is the Docosahexaenoic acid with a value of 2.297%. The most abundant polyunsaturated fatty acid recorded is Linoleic acid (2.075 while the least abundant polyunsaturated fatty acid was eicosapentaenoic acid (EPA, C20:5n-3). There was significant variation (p < 0.05) in the level of Docosahexaenoic acid and Eicosapentaenoic acid in the fish species. The monounsaturated fatty acids (MUFA) content of horse mackerel was mainly omega-9 fatty acids except Palmitoleic acid which is an omega-7 fatty acid. It can be concluded that the horse mackerel has a good mineral and fatty acid profiling.