This study formulates a qualitative image-based approach to establishing cetacean sightings’ effort at an ecosystem scale in the Gulf of Maine. As a first step, I investigate a rare set of long-term sightings (2008–2017, the study period) of a male killer whale (Orcinus orca) representing unusually consistent occurrences, without considering observation effort. Largely unknown, killer whale populations in the NW Atlantic are tiny, travelling over vast areas, and at risk of human-caused extinction. The synthesis uses opportunistic observations, reported mainly by recreational mariners and commercial fishers incorporated into data manipulations anonymously. Adding an effort index using the qualitative image-based approach, I then investigate the hypothesis that the killer whale sightings constitute seasonal-spatial fidelity to the greater GoM, the first documentation of fidelity patterns in the western Atlantic hemisphere. The analysis includes comparisons to frequency distributions of single killer whales in the gulf in the historical past as a baseline, i.e. post mid 1940s. Finally, the fidelity analysis reveals a substantial spatial anomaly in the recent sightings data for the northeastern GoM. An explanation for the emergent anomaly is pursued by analyses of indicators of the availability of Atlantic herring (Clupea harengus) [fisheries landings, Atlantic puffin (Fratercula arctica) chick diets] as potential prey in the NE gulf. With the development of complementary corroborative approaches to the analysis of incidental sightings, it is possible to chip away at impediments to the understanding of ecosystem attractants and deterrents with respect to cetacean distributions.

The world’s fisheries and aquaculture industries produce vast amounts of protein-containing by-products that can be enzymatically hydrolysed to smaller peptides and possibly be used as additives to functional foods and nutraceuticals targeted for patients with obesity-related metabolic disorders. To investigate the effects of fish protein hydrolysates on markers of metabolic disorders, obese Zucker fa/fa rats consumed diets with 75 % of protein from casein/whey (CAS) and 25 % from herring (HER) or salmon (SAL) protein hydrolysate from rest raw material, or 100 % protein from CAS for 4 weeks. The fatty acid compositions were similar in the experimental diets, and none of them contained any long-chain n-3 PUFA. Ratios of lysine:arginine and methionine:glycine were lower in HER and SAL diets when compared with CAS, and taurine was detected only in fish protein hydrolysate diets. Motifs with reported hypocholesterolemic or antidiabetic activities were identified in both fish protein hydrolysates. Rats fed HER diet had lower serum HDL-cholesterol and LDL-cholesterol, and higher serum TAG, MUFA and n-3:n-6 PUFA ratio compared with CAS-fed rats. SAL rats gained more weight and had better postprandial glucose regulation compared with CAS rats. Serum lipids and fatty acids were only marginally affected by SAL, but adipose tissue contained less total SFA and more total n-3 PUFA when compared with CAS. To conclude, diets containing hydrolysed rest raw material from herring or salmon proteins may affect growth, lipid metabolism, postprandial glucose regulation and fatty acid composition in serum and adipose tissue in obese Zucker rats.

Dietary intervention studies to assess the cardioprotective effects of oily fish are scarce in China. The present study aimed to examine the effects of the oily fish, Norwegian salmon, herring and local farmed pompano (Trachinotus ovatus) on CVD risk markers when included in the Chinese diet. In this 8-week, parallel-arm, randomised intervention study, 126 Chinese women with hypertriacylglycerolaemia, aged 35–70 years, were assigned to four groups to consume an experimental lunch containing 80 g fillets of either one of three oily fish or a mix of commonly eaten meats (pork/chicken/beef/lean fish) for 5 d/week. The results showed that inclusion of the three oily fish significantly increased the intake of n-3 long-chain PUFA (LC-PUFA) while decreasing the dietary n-6:n-3 PUFA ratio. Compared to the control group, significant increases of DHA, EPA+DHA and total n-3 PUFA in plasma choline phosphoglyceride were observed in the three oily fish groups. Plasma TAG levels were significantly reduced only in the salmon and herring groups. When compared to the baseline level, the three oily fish diets significantly decreased serum concentrations of TAG, apoB, apoCII and apoCIII, but only the salmon and herring diets significantly lowered TNF-α and raised adiponectin levels in serum. The salmon diet additionally decreased the serum concentration of IL-6. To conclude, dietary inclusion of salmon, herring and pompano as oily fish can effectively increase serum n-3 LC-PUFA content and are associated with favourable biochemical changes in dyslipidaemic middle-aged and elderly Chinese women, and these beneficial effects are mainly associated with n-3 LC-PUFA contents.

The design and evaluation of survey-based management strategies is addressed in this article, using three case-study fisheries: North Sea herring, Bay of Biscay anchovy and North Sea cod, with a brief history and the main management issues with each fishery outlined. A range of operational management procedures for the case study stocks were designed and evaluated using trends that may be derived from survey indices (spawner biomass, year-class strength and total mortality) with an array of simple and more structured observation error regimes simulated. Model-free and model-based indicators of stock status were employed in the management procedures. On the basis of stochastic stock-specific simulations, we identified the following key determinants of successful management procedures: (i) adequate specification of the stock-recruit relationship (model structure, parameter estimates and variability), (ii) knowledge of the magnitude and structure of the variation in the survey indices, and (iii) explication of the particular management objectives, when assessing management performance. More conservative harvesting strategies are required to meet specified targets in the presence of increasing stochasticity, due to both process and observation error. It was seen that survey-based operational management procedures can perform well in the absence of commercial data, and can also inform aspects of survey design with respect to acceptable levels of error or bias in the surveys.

Previously undescribed cystophorous cercariae which develop in sporocyst germinal sacs in the tectibranch opisthobranch Philine denticulata (Adams) are shown to be cercariae of Hemiurus luehei Odhner, 1905 (Hemiuridae), a common stomach parasite of clupeid and salmonid fishes off the Atlantic coast of Europe, in the Baltic and the Mediterranean Sea. The free-swimming cercariae are seized by calanoid copepods. Temora longicornis (Müller) and Acartia tonsa Dana acted as suitable experimental intermediate hosts. Pressure by the copepod mouth appendages causes delivery tube eversion and the injection of the cercarcial body into the haemocoel. Sagitta sp. was found naturally infected with a metacercaria of H. luehei. The cystophorous cercaria and metacercaria are described using light and scanning electron microscopy. Adults from herring were examined under the stereoscan electron microscope.

Diel variations in schooling patterns and spatial dynamics during spawning were studied in Norwegian spring-spawning herring (Clupea harengus) off south-western Norway by acoustic surveying, diel cycle experiments and school tracking by sonar, and bottom gillnet sampling. Herring formed horizontally extensive, loosely packed demersal layers shortly after darkness. At night, the fish disappeared in the acoustic dead zone, but lifted off the bottom early in the following mornings. At daytime the herring reorganised into dense pelagic schools. The evening descent to the spawning habitat was considered as part of a precautionary strategy towards visual predators, as the bottom is a high-risk zone for archetypal pelagic fish like herring. Large numbers of gadoids, which are potential herring predators, were present in the area. Herring not ready to spawn dominated the bottom samples in 4 out of 5 days, suggesting that pre-spawning herring followed the descent of ripe herring. The herring spawning layers shifted in a south-easterly direction from day to day in diel spawning waves.

This study investigates whether pelagic fish schools of different species or groupings (e.g. herring, "surface herring", "gadoids", mackerel, sprat and sandeels) were positively or negatively associated with each other in time and space. To do this, statistical models were fitted to pre-processed acoustic fisheries data to reveal how pelagic school prevalence varied with respect to spatial (latitude and longitude) and temporal (time of day) information. The model outputs, which take the form of probabilities fitted to the presence or absence of schools, were then used to calculate correlation coefficients, which are useful for measuring association between pairs of variables. Results depended upon the specific species pairs under investigation. Herring and "surface herring" were, for example, very generally sympatrically associated with each other in both space and time, while herring and gadoid schools, on the other hand, had allopatric distributions.

In the herring (Clupea harengus), the swim bladder is connected to both the alimentary canal and the anal opening. The anterior duct is used for filling the swim bladder with air. Gas release from the anal opening is often observed when the fish is scared or during ascent and descent. Here, the sounds produced by such a gas release are studied. The fish was kept in a low-pressure chamber. As the ambient pressure was reduced, the gas in the swim bladder expanded and was emitted through the anal opening. Herring sounds were also recorded in a fish trap and in the field. The characteristic sound made by herring during gas release is denoted as the pulsed chirp. This pulsed chirp is 32–133 ms long (N = 11) and consists of a series of 7–50 (N = 11) transient pulses with a continuous reduction of the frequency emphasis (centroid frequency of first pulse 4.1 kHz and of last pulse 3.0 kHz, N = 11). The source level of the chirp is 73 ± 8 dB re 1 μPa rms (root mean square) at 1 m (N = 19). The pulsed chirp is not known to be produced by any other marine animal and may be a good fingerprint for identifying schools of clupeid fish by natural predators, fishery scientists and fishermen. A model for the generation of the pulsed chirp is presented and tested on existing data.

The underwater sound of R/V "Johan Hjort" as a function of aspect angle has been mapped by cruising along parallel transects at various distances from the recording unit. At frequencies over 125 Hz there was a minimum in front of the vessel, and lobes of higher intensity on both sides. About 20% of the herring schools recorded during a survey in the North Sea seemed to react to the survey vessel. The distance at which the schools reacted varied from about 25 m and up to about 1000 m in front of the vessel. Within a sector of 20° on each side of the path of the vessel, the fraction of schools reacting increased to about 50%. Most of the schools that reacted seem to be herded in front of the vessel. This reaction pattern may indicate either that the schools reacted to the higher sound intensity to the side of the vessel or that the pattern occurred because of a "pursuit effect". Despite the apparent herding, more than 40% of the schools in front of the vessel were not recorded by the echo sounder. It is therefore argued that horizontal avoidance close to the vessel may have caused an underestimation of the biomass of herring of about 20%.

A method for acoustic abundance estimation by horizontal guided sonar of fish schooling close tosurface is presented. The basic principle is to measure the horizontal area of schools in situ, and derive the school biomass subsequently through a school area to school biomass relationship. The application of the method is exemplified through a sonar survey in the eastern North Sea-Skagerrak in September 1990. The areas of recorded schools were measured by the estimate function of a Furuno CSH-70 sonar, and selected schools were captured by purse seine to establish a school-area to school-biomass relationship. In the actual region, the biomass of herrig (Clupea harengus) and mackerel (Scomber scombrus) was estimated to about 90 000 and 43 0000 tons, respectively. The accuracy of the method is discussed and improvements are suggested.