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A unique 16-year time series of deep video surveys in Monterey Bay reveals that the Humboldt squid, Dosidicus gigas, has substantially expanded its perennial geographic range in the eastern North Pacific by invading the waters off central California. This sustained range expansion coincides with changes in climate-linked oceanographic conditions and a reduction in competing top predators. It is also coincident with a decline in the abundance of Pacific hake, the most important commercial groundfish species off western North America. Recognizing the interactive effects of multiple changes in the environment is an issue of growing concern in ocean conservation and sustainability research.invasive species ͉ top predators ͉ top-down forcing O ne of the greatest challenges in contemporary ocean science is that of predicting how oceanic communities will respond to impending changes, such as climatic warming and the removal of top predators (1). Interactive changes are of particular concern, but little information is available on the collateral effects of multiple factors. Rising temperatures have been implicated in shifting the geographical distribution patterns of fishes and plankton (2, 3) and in the disruption of plankton communities (4, 5). Removing top predators from an ecosystem can result in a cascade of effects that restructures the food web at lower trophic levels (6, 7) as well as at the top (8). Together, two or more such changes may act in ways that we cannot yet predict (9).Here we demonstrate that the Humboldt squid, Dosidicus gigas, has greatly extended its perennial range in the eastern North Pacific Ocean. This geographic expansion occurred during a period of ocean-scale warming, regional cooling, and the decline of tuna and billfish populations throughout the Pacific (10). In this case, environmental changes off California are concurrent with invasion by a species from an adjacent region. Examples of invasion by species at higher trophic levels are relatively rare. The subsequent ecological impact of the Humboldt squid invasion can be seen in possible top-down forcing on the local population of Pacific hake, but the ecological effects may not yet be fully expressed (11). The question of how an oceanic community will respond to climatic change must include the possibility of invading species (12), and the consequences of removing top predators may depend on whether there is an ecological understudy waiting in the wings. Dosidicus (Fig. 1) is a large, aggressive, abundant pelagic squid that reaches mantle lengths of 1.2 m, overall lengths Ͼ2 m, and weights up to 50 kg. Its geographical distribution is centered in the eastern equatorial Pacific. From these warm waters, its historical range extends along the subtropical coasts of both North and South America, with episodic but temporary range extensions to latitudes as high as 40°(13). Only a single species is known, although genetic evidence suggests that northern and southern populations are diverging (13,14). Dosidicus feeds opportunistically on a bro...

Artículo de publicación ISISome 290 species of squids comprise the order Teuthida that belongs to the molluscan Class Cephalopoda. Of these, about 30-40 squid species have substantial commercial importance around the world. Squid fisheries make a rather small contribution to world landings from capture fisheries relative to that of fish, but the proportion has increased steadily over the last decade, with some signs of recent leveling off. The present overview describes all substantial squid fisheries around the globe. The main ecological and biological features of exploited stocks, and key aspects of fisheries management are presented for each commercial species of squid worldwide. The history and fishing methods used in squid fisheries are also described. Special attention has been paid to interactions between squid fisheries and marine ecosystems including the effects of fishing gear, the role of squid in ecosystem change induced by overfishing on groundfish, and ecosystem-based fishery management

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SUMMARYWe studied the locomotion and behavior of Dosidicus gigas using pop-up archival transmitting (PAT) tags to record environmental parameters (depth, temperature and light) and an animal-borne video package (AVP) to log these parameters plus acceleration along three axes and record forward-directed video under natural lighting. A basic cycle of locomotor behavior in D. gigas involves an active climb of a few meters followed by a passive (with respect to jetting) downward glide carried out in a finsfirst direction. Temporal summation of such climb-and-glide events underlies a rich assortment of vertical movements that can reach vertical velocities of 3ms , characteristic of the midwater oxygen minimum zone (OMZ), can influence the daytime depth of squid, but this depends on location and season, and squid can ʻdecoupleʼ from this environmental feature. Light is also an important factor in determining daytime depth, and temperature can limit nighttime depth. Vertical velocities were compared over specific depth ranges characterized by large differences in dissolved oxygen. Velocities were generally reduced under OMZ conditions, with faster jetting being most strongly affected. These data are discussed in terms of increased efficiency of climband-glide swimming and the potential for foraging at hypoxic depths.

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Little is known about embryonic development of oceanic squids, yet such information is critical to a meaningful understanding of these ecologically and economically important species. Eggs of the Humboldt squid Dosidicus gigas were artificially fertilized and incubated at temperatures found throughout this species' range (5 to 30°C). Successful development through hatching was observed only between 15 and 25°C, and the rate of development increased with increasing temperature. Previous work reported a D. gigas egg mass at the pycnocline in the Gulf of California, suggesting that successful embryonic development can occur only in those areas of the eastern Pacific where temperature at the pycnocline is between 15 and 25°C. Analysis of available oceanographic data revealed a vast area relatively close to the California coast that is seasonally suitable for development of D. gigas embryos. Spawning offshore in this region may thus be an important factor supporting the D. gigas populations that invaded coastal waters of the Pacific Northwest after 2005. KEY WORDS: Development · Dosidicus gigas · Humboldt squid · Temperature effects · In vitro fertilization · Range expansion · Parthenogenesis Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 441: [165][166][167][168][169][170][171][172][173][174][175] 2011 agarose with a more natural material created from the freeze-dried accessory nidamental glands of L. pealeii and obtained chorion expansion in 4 oceanic squid species, one of which (Sthenoteuthis oualaniensis) produced viable hatchlings.Attempts to identify an analogous natural material from an ommastrephid rather than a loliginid source revealed that only material from oviducal glands was effective in supporting chorion expansion (Sakurai & Ikeda 1994, Ikeda & Shimazaki 1995. The use of oviducal gland material led to successful development through hatching of artificially fertilized embryos of Todarodes pacificus (Sakurai & Ikeda 1994, Watanabe et al. 1996, Sthenoteuthis ouala ni ensis and Omma strephes bartramii (Sakurai et al. 1995), and Dosidicus gigas (Yatsu et al. 1999). Despite these successes, little subsequent work has been carried out on artificially fertilized eggs of ommastrephid species (Staaf et al. 2008).Embryonic development of Dosidicus gigas and its temperature dependence is of particular interest in the context of the recent northward range expansion of this large predator in the California Current system over the past decade (Zeidberg & Robison 2007). Adults have been shown to consume a wide variety of fish, crustaceans, and molluscs , Field et al. 2007), some of which are of considerable ecological and commercial importance (Field et al. 2010). Although adults of D. gigas appear to have become abundant in the California Current, whether they spawn in these relatively cold waters or migrate to warmer waters to spawn is unknown. Spawning areas for D. gigas have been reported in the Gulf of California (Gilly et al. 2006a, Camarillo-Coop e...

Like many other loliginid squid, Doryteuthis (Loligo) opalescens deposits egg cases on the ocean floor. Depending upon temperature, egg cases may persist for 5–12 weeks before the paralarvae hatch. Because of this relatively long duration and squid’s pelagic life history, egg cases provide a practical life stage to survey. During 2001–2002, squid egg beds in Monterey Bay, Carmel Bay, and around the California Channel Islands were surveyed using a remotely operated vehicle with the goal of delineating the habitat of egg beds that are spawned during active commercial fishing. Egg cases were highly aggregated and densities reached 1338 capsules m−2. Squid eggs were significantly shallower in Central California. Egg cases occurred between 20 and 93 m around the Channel Islands, and in Central California they were between 13 and 61 m. The temperatures in both regions were similar (10–12 °C), with some eggs in Southern California found up to 14.4 °C. Ninety‐five percent of eggs were found on sand, suggesting that temperature and substrate are stronger behavioral cues than depth to stimulate spawning. Suitable spawning habitat was defined by three criteria: sandy benthic substrate, temperatures between 10 and 14.4 °C, and depths between 20 and 70 m when the first two criteria hold. Additionally, within this defined area, oxygen concentration is quantified. The greatest commercial landings of market squid occur in both Central and Southern California during a time of year when water temperatures of 10–12 °C are prevalent in the 20–70 m depth range.