Scale Analysis Suggests Frequent Skipping of Second Reproductive Season in Atlantic Herring

A common assumption in fish studies is that iteroparous fish, once mature, normally reproduce in all consecutive seasons. Analysis of scales from Norwegian spring-spawning herring collected between 1935-1973 revealed strong under-representation (47% of expected) of second-time spawners on the spawning grounds. This reduction is not explained satisfactorily by possible errors in scale-reading, suggesting that the second reproductive season is frequently skipped. Skipping a season may relate to trade-offs between growth, current and future reproduction, and survival, which are likely to be particularly strong for young adult herring

Resolving climate impacts on fish stocks

Evidence is accumulating that the increase in CO2 is affecting the global climate, with far‐reaching implications for biological processes and ecosystem services. Recent studies suggest that there is evidence for a northward shift in the distributional range of fish species, but the mechanisms underlying these changes remain uncertain. Hence, it is largely unknown whether the observed distributional shifts are caused by a relocation of the spawning and feeding grounds, a change in the local survival of fish, or immigration into new habitats

Evolutionary impact assessment: accounting for evolutionary consequences of fishing in an ecosystem approach to fisheries management

Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). while the number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently in fisheries-induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life-history traits, behavior, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause fisheries-induced evolution with effects accumulating over time. Consequently, FIE may alter then utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons, An important reason this is not happening is the lack of an appropriate assessment framework. We therefor describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary outcomes of alternative management options. EvoIA can contribute to the ecosystem approach to fisheries management by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries

Maintenance Therapy With Tumor-Treating Fields Plus Temozolomide vs Temozolomide Alone for Glioblastoma: A Randomized Clinical Trial.

IMPORTANCE: Glioblastoma is the most devastating primary malignancy of the central nervous system in adults. Most patients die within 1 to 2 years of diagnosis. Tumor-treating fields (TTFields) are a locoregionally delivered antimitotic treatment that interferes with cell division and organelle assembly. OBJECTIVE: To evaluate the efficacy and safety of TTFields used in combination with temozolomide maintenance treatment after chemoradiation therapy for patients with glioblastoma. DESIGN, SETTING, AND PARTICIPANTS: After completion of chemoradiotherapy, patients with glioblastoma were randomized (2:1) to receive maintenance treatment with either TTFields plus temozolomide (n = 466) or temozolomide alone (n = 229) (median time from diagnosis to randomization, 3.8 months in both groups). The study enrolled 695 of the planned 700 patients between July 2009 and November 2014 at 83 centers in the United States, Canada, Europe, Israel, and South Korea. The trial was terminated based on the results of this planned interim analysis. INTERVENTIONS: Treatment with TTFields was delivered continuously (>18 hours/day) via 4 transducer arrays placed on the shaved scalp and connected to a portable medical device. Temozolomide (150-200 mg/m2/d) was given for 5 days of each 28-day cycle. MAIN OUTCOMES AND MEASURES: The primary end point was progression-free survival in the intent-to-treat population (significance threshold of .01) with overall survival in the per-protocol population (n = 280) as a powered secondary end point (significance threshold of .006). This prespecified interim analysis was to be conducted on the first 315 patients after at least 18 months of follow-up. RESULTS: The interim analysis included 210 patients randomized to TTFields plus temozolomide and 105 randomized to temozolomide alone, and was conducted at a median follow-up of 38 months (range, 18-60 months). Median progression-free survival in the intent-to-treat population was 7.1 months (95% CI, 5.9-8.2 months) in the TTFields plus temozolomide group and 4.0 months (95% CI, 3.3-5.2 months) in the temozolomide alone group (hazard ratio [HR], 0.62 [98.7% CI, 0.43-0.89]; P = .001). Median overall survival in the per-protocol population was 20.5 months (95% CI, 16.7-25.0 months) in the TTFields plus temozolomide group (n = 196) and 15.6 months (95% CI, 13.3-19.1 months) in the temozolomide alone group (n = 84) (HR, 0.64 [99.4% CI, 0.42-0.98]; P = .004). CONCLUSIONS AND RELEVANCE: In this interim analysis of 315 patients with glioblastoma who had completed standard chemoradiation therapy, adding TTFields to maintenance temozolomide chemotherapy significantly prolonged progression-free and overall survival. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00916409

One Hundred and Twenty Years of Change in Fishing Power of English North Sea Trawlers

Fishing vessels differ in fishing power-that is, in the quantity of fish they would catch per unit time if they were fishing at the same time and location-and there is a general trend of increasing fishing power over time. Typically, fishing power studies are limited to comparisons over 1-2 decades, but here I attempt to quantify this trend for English North Sea trawlers over the past 120 years. A review of fishing history shows how sailing trawlers, steam trawlers, and currently both motor otter trawlers and twin-beam trawlers have in turn dominated the trawl fisheries. A huge, overall increase in fishing power has occurred but the trend has been all but linear: fishing power has sometimes "leapt" forward within a few years, but at times has also stagnated for decades. Compared with historical sailing trawlers, motor otter trawlers around the Millennium are estimated to have 50 times higher cod fishing power, and twin-beam trawlers to have 100 times higher plaice fishing power. However, this does not mean that fisheries have become more profitable, because increases in catch rates have lagged far behind those in fishing power, and everything points in the direction of great overcapacity of the current international North Sea trawling fleet

Ideal free distribution or dynamic game?:An agent-based simulation study of trawling strategies with varying information

An ecological economic model of trawling is presented to demonstrate the effect of trawling location choice strategy on net input (rate of economic gain of fish caught per time spent less costs). Fishing location choice is considered to be a dynamic process whereby trawlers chose from among a repertoire of plastic strategies that they modify if their gains fall below a fixed proportion of the mean gains of the fleet as a whole. The distribution of fishing across different areas of a fishery follows an approximate ideal free distribution (IFD) with varying noise due to uncertainty. The least-productive areas are not utilised because initial net input never reaches the mean yield of better areas subject to competitive exploitation. In cases, where there is a weak temporal autocorrelation between fish stocks in a specific location, a plastic strategy of local translocation between trawls mixed with longer-range translocation increases realised input. The trawler can change its translocation strategy in the light of information about recent trawling success compared to its long-term average but, in contrast to predictions of the Marginal Value Theorem (MVT) model, does not know for certain what it will find by moving, so may need to sample new patches. The combination of the two types of translocation mirrored beam-trawling strategies used by the Dutch fleet and the resultant distribution of trawling effort is confirmed by analysis of historical effort distribution of British otter trawling fleets in the North Sea. Fisheries exploitation represents an area where dynamic agent-based adaptive models may be a better representation of the economic dynamics of a fleet than classically inspired optimisation models. Crow

Maturity changes in Norwegian spring-spawning herring Clupea harengus:Compensatory or evolutionary responses?

The stock of Norwegian spring-spawning herring Clupea harengus collapsed to a state of commercial extinction in the 1960s, probably due to both overexploitation and unfavourable climatic conditions. Since the 1980s, the stock has fully recovered. Following the collapse, the fish matured at much earlier ages and somewhat larger sizes than previously. Currently, age and size at 50% maturity have only to some extent returned to pre-collapse levels. Two non-exclusive hypotheses that may account for the maturity changes are (1) the 'compensatory response' hypothesis, predicting that reduced stock size resulting from exploitation leads to faster growth and hence earlier maturity as a phenotypically plastic response to environmental change; and (2) the 'evolutionary response' hypothesis, predicting that intensive exploitation causes selection for early maturation, since few late-maturing phenotypes survive until first spawning. Trends in length-at-age suggest a strong compensatory response, but leave the possibility of evolutionary change unaddressed. In order to disentangle phenotypic and possible genetic changes in maturation, we examined the reaction norm for age and size at maturation to see if any changes had occurred. This reaction norm describes the probabilities of maturing at each relevant age and size. We found small but statistically significant changes in maturation reaction norms; these changes were restricted to 2 out of 6 of the maturation ages. This confirms that growth-related phenotypic plasticity has largely been responsible for the documented changes in maturity, and suggests at most a weak evolutionary response. This is in line with theoretical expectations from the dominating fishing pattern, where pure schools of only mature or only early immature fish were targeted, rather than a fishery on both immature and mature fish simultaneously, as has been the case in stocks of cod Gadus morhua and plaice Pleuronectes platessa, where significant evolutionary responses have been found

Dynamics in frequency of skipped reproduction in Norwegian spring-spawning herring

A common presumption in fisheries science is that adult iteroparous fish, once matured, typically spawn in all consecutive years. Recent evidence suggests, however, that skipping of reproduction occurs more commonly than is usually believed. Adult Norwegian spring-spawning herring (Clupea harengus) undertake long annual migrations between feeding, overwintering, and spawning areas. Analysis of extensive historical data on scales suggested that, on average, almost one in two herring may skip their second spawning migration. Moreover, the frequency of skipping may vary considerably from year to year. Based on annual variations in skipped reproduction, relationships are examined here between the mean weight and condition of spawning herring in a given year, and the fraction of fish skipping the second reproductive season in the following year. Environmental influences on skipping are examined based on indices of annual temperature and zooplankton abundance in the Norwegian Sea. The results corroborate with the hypothesis that skipped reproduction results from trade-offs between current and future reproduction, growth and survival: participation in distant, energetically costly and risky spawning migrations may only pay off in terms of fitness if individuals are sufficiently large and in sufficient condition to both successfully migrate and spawn