Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimate global forage fish contributions to marine ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: (i) the ecological support service of forage fish to predators in marine ecosystems, (ii) the total catch and value of forage fisheries and (iii) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied and exhibited patterns across latitudes and ecosystem types. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Overall, forage fish contribute a total of about $16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex‐vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was $5.6 billion, fisheries supported by forage fish were more than twice as valuable ($11.3 billion). These estimates provide important information for evaluating the trade‐offs of various uses of forage fish across ecosystem types, latitudes and globally. We did not estimate a monetary value for supportive contributions of forage fish to recreational fisheries or to uses unrelated to fisheries, and thus the estimates of economic value reported herein understate the global value of forage fishes.

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Harmful algal blooms (HABs) caused by the dinoflagellate Cochlodinium polykrikoides have increased in geographic extent, frequency, and duration in coastal areas worldwide. These blooms have negatively impacted many coastal fisheries, causing mass mortalities of both wild and farmed fish. Forage fish species may be particularly susceptible to HABs as they feed on plankton and are highly abundant in coastal ecosystems where these blooms occur. While mortalities associated with HABs have been well documented for juvenile and adult fish, the potential impacts to early life stages (i.e. embryos and eleutheroembryos) have not been explored. We conducted a series of toxicity experiments using a clonal laboratory culture of C. polykrikoides and 3 forage fish species (Atlantic silverside Menidia menidia, inland silverside M. beryllina, and sheepshead minnow Cyprinodon variegatus) all common on the US East Coast. Our experiments demonstrated that C. polykrikoides caused mortalities in both embryos and eleutheroembryos, but that sensitivity to acute toxicity differed among fish species (M. beryllina > M. menidia > C. variegatus) and among life stages (eleutheroembryos > embryos). Although embryos were somewhat resistant to C. polykrikoides biotoxins until they hatched, once they hatched, they experienced rapid mortality and impaired swimming ability. By testing ecologically relevant exposure times to C. polykrikoides, we found that eleutheroembryos can become incapacitated relatively quickly (i.e. within hours), and that surviving fish could recover swimming ability following removal from C. polykrikoides exposure. This research provides the first evidence of sublethal impacts on fish exposed to C. polykrikoides, and advances understanding of the potential ecosystem impacts of this harmful alga.

Hydrological regimes are significant drivers of fisheries production in many African Lakes due to their influence on fish habitat and food availability, breeding success, and catchability. Lake Turkana, Kenya, will undergo substantial changes in hydrology due to water regulation and extraction along the Omo River in neighboring Ethiopia, which provides over 90% of its water. The objective of this study was to predict how the lake's fisheries, which provide an important livelihood and protein source in the region, will respond to hydrological change. While variations in fishing effort are poor predictors of fisheries catch in the lake, water levels and their fluctuations strongly influence fisheries production. Seasonal oscillations play a particularly important role, and with complete loss of these oscillations, the lake's predicted fisheries yield will decrease by over two thirds. The fishery is predicted to collapse at a lake level decline of 25 m, regardless of seasonal amplitude magnitude. The lake's total littoral habitat, where fisheries are currently concentrated, will increase in surface area with lake level declines of <25 m. However, the extent of productive, dynamic littoral habitat will decrease with dampening of the lake's seasonal oscillations. The most severe habitat loss will occur in the lake's Turkwel Sector, which hosts the region's highest human population densities, and North Sector, where inter‐tribal conflict over resources is common and likely to be exacerbated by lake level decline. The continued ecological functioning of Lake Turkana necessitates immediate efforts to develop and apply a water resource management plan rooted in science.

Blooms of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides present both lethal and sublethal threats to coastal marine organisms. Because prior studies of this harmful algal bloom (HAB) species have focused on its acute toxic effects on fish, there remains a limited understanding of the sublethal effects on the swimming behavior of fish when exposed to these blooms. We conducted a video‐based laboratory assessment of the effects of C. polykrikoides exposures on larval and juvenile fish swimming behavior. Juvenile and larval life stages of three forage species common to the U.S. East Coast were examined: wild Atlantic Silversides Menidia menidia, hatchery‐reared Inland Silversides M. beryllina, and hatchery‐reared Sheepshead Minnow Cyprinodon variegatus. Results showed that juvenile Atlantic Silversides and Inland Silversides exposed to C. polykrikoides concentrations of 102 cells/mL swam significantly further distances in comparison with their baseline (control) behavior. In an ecosystem context, the results of this research support field‐based studies demonstrating that when blooms of this HAB species are present, the relative abundance of fish declines (i.e., the fish presumably detect the blooms and swim away after exposure). Conversely, juvenile Sheepshead Minnow exhibited no increased swimming behavior when exposed, supporting previous studies indicating that this species is more resistant to C. polykrikoides toxicity. Importantly, no behavioral changes were found in experiments with larval conspecifics (i.e., Inland Silversides and Sheepshead Minnow), suggesting that younger life stages, which lack developed gills and olfactory systems, may be unable to detect the dinoflagellate. This clear ontogenetic difference implies that for certain fish species, reaching later life stages may provide a refuge to HAB toxicity. Received March 26, 2017; accepted June 5, 2017 Published online August 9.2017

) to large-scale (1000 t yr −1 ) fish production, respectively. On both islands, the seagrass variables, shoot productivity, standing crop and leaf morphometrics (length and width) were significantly lower (p < 0.0001) in impacted seagrass patches adjacent to fish farms compared with control patches. In addition, significantly higher sea urchin densities and herbivore feeding pressure (percentage of shoots with herbivore grazing scars) were found in impacted patches on both islands. Higher leaf tissue nitrogen and epiphyte loads were also found in impacted patches, but these increases could not be attributed to fish farming alone. Our results show that negative effects on seagrass patches can occur as a result of fish farming at both small-scale and large-scale intensities and that increased sea urchin densities and feeding pressures are important indirect effects of coastal aquaculture on these islands.

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