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Proposal for a Habitat Area of Particular Concern for Juvenile Atlantic Cod (Gadus morhua)
in the Nearshore Waters of the Gulf of Maine Prepared by New England Fishery Management Council's Essential Fish Habitat Technical Team Habitat Considerations (Excerpted from Habitat Annual Review Report 5) Table of Contents (Click Back Button to return to table of contents) * Recent Research
=================================================== ------------------------------------------------------------------------------ Inshore GOM HAPC page 3 Juvenile Cod Community & Interactions - Research Results Pelagic Juvenile Settlement Post-larval pelagic juveniles are transported by prevailing currents to shallow waters off eastern Newfoundland beginning in May and may continue arriving in periodic pulses as late as December (Methven and Bajdik 1994; Grant and Brown 1998). Their length upon settlement is 25-45 mm (Pinsent and Methven 1997). In southwest Nova Scotia, pelagic juveniles arrive inshore slightly larger (~40-50 mm) in May (Tupper and Boutilier 1995a and 19951,), whereas influxes of larvae begin earlier in Massachusetts waters two to three months after hatching (Bigelow and Schroeder 1953). On Georges Bank, cod settle out in July at 40-60 mm, and those reaching rough and cobble bottom may experience reduced predation risk. This particular habitat may be an important demographic bottleneck to benthic recruitment on Georges Bank (Loughetal. 1989). Pelagic juveniles exhibit no preference for habitat types at settlement, and they occupy rock reef, cobble, eelgrass (Zostera marina) beds, and sand bottom (Tupper and Boutilier 199 Sb). Tupper and Boutilier (1995b) assumed that settling also occurred on macroalgae habitat, as noted by Keats et al. (1987) off eastern Newfoundland, however, algal stands were scarce in the St. Margaret's Bay, Nova Scotia, study area due to subtidal grazing by sea urchins (Strongylocentrotus drobachiensis). Sea urchins commonly leave a partially denuded or "barren" zone along nearshore sections of the maritime provinces and Gulf of Maine. -------------------------------------------------------------------------- Inshore GOM HAPC page 4 inversely related to the index of rugosity. As a result, higher densities of age-C cod were found in cobble and rock reef habitats than in eelgrass. However, the rugosity index could not account for the complexity of surface area that eelgrass offered. Higher survival in sites of cobble and rock reef was attributed to increased shelter that the more structurally complex habitats afforded coupled with decreased predator efficiency (Keats et al. 1987; Lough et al. 1989; Tupper and Boutilier 1995b; Gotceitas et al. 1997; Grant and Brown 1998a and 1998b). Tupper and Boutilier's (1995b) and Grant and Brown's (1998a) in situ studies confirmed earlier and subsequent laboratory experiments on substrate preference and predator efficiency. Clearly, the presence of conspecifics may influence the distribution and food intake of age-C cod in the wild. Both age-C and 1 cod preferred finer grained substrate in absence of a predator, but when in the presence of an age-3 conspecific, young-of-the-year and age-i either avoided the predator or selected the coarser substrate (cobble vs. gravel) where they hid in interstitial spaces (Gotceitas and Brown 1993; Gotceitas et al. 1995; Fraser et al. 1996). Age-C avoided the yearling conspecific resulting in a significant increase in use of gravel and cobble confirming the level of habitat segregation noted in the wild (Fraser et al. 1996). Also, age-O cod avoided kelp (Lam maria) except when exposed to an actively foraging predator and cobble was unavailable. In this situation, kelp significantly reduced predation risk (Gotceitas et al. 1995). Both field and laboratory studies indicate that the association with coarse substrates, when coupled with behavior patterns that reduce predation risk, give young cod competitive advantage in avoiding detection or capture. Eelgrass Habitat and Abiotic Factors
--------------------------------------------------------- Inshore GOM HAPC page 5 Among-Habitat Variation in Age-O Growth
Among-Habitat Variation in Age-O Survival
Mark-recapture experiments indicate age-0 cod remain very localized, not moving more than several hundred meters in both eelgrass and no-eelgrass habitats (Grant and Brown 1998b). Those that settled earliest and were largest at settlement grew faster and defended a larger territory than later! smaller settlers (Tupper and Boutilier 1995 a), thus a competitive advantage in growth and survival may exist for the earliest pulse of post-larval juveniles over those settling later when temperatures and day length are reduced (Tupper and Boutilier 1995b). Abundance in the seagrass sites of St. Margaret's Bay, Nova Scotia, was noted to decline after early June. This was attributed to predation rather than emigration because young were strongly site-attached and defended territory as they grew. Marked individuals were not found in areas surrounding the study site (Tupper and Boutilier 199 Sb). As the summer season advanced, a greater decline in abundance occurred in eelgrass beds and on sand than in structurally more complex reef and cobble habitat. Observing in situ young-of-the-year seeking shelter in rock crevices, empty scallop shells, and other debris within dense grass beds, Tupper and Boutilier (1995b) believed that cod out-grew eelgrass blades as suitable refuge. ---------------------------------------------------------------- Inshore GOM HAPC page 6 Unable to compete for nonexistent shelter on sand habitat, age-0 cod school for protection (Tupper and Boutilier 1995a); however, the population density in these areas reached zero by late June (Tupper and Boutilier I 995b). Predation by three Cottids - sea raven (Hemitripterus americanus), grubby (Myoxocephalus aeneus) , and longhorn sculpin (Myoxocephalus octodecemspinosus) - was most successful on sand and least successful on cobble and rock reef. Age-O cod schooling over sand bottoms have low site fidelity which is disadvantageous to survival (Grant and Brown 1998a). Young-of-the-year appear to lose site fidelity and disperse into deeper water during the December-January period (Tupper and Boutilier 1995a; Gregory and Anderson 1997) adopting winter behavior of reduced activity and food consumption (Brown et al. 1989). Still, some marked demersal juveniles remained localized in the shallowest (<1.2 m) sampling site in Trinity Bay, Newfoundland, throughout the winter even when ice was present (Grant and Brown 1998b). Age-0 and older juveniles are more adapted than adult cod to survive icy subzero water due to elevated plasma antifreeze levels in their blood (Goddard et al. 1992). Age-1 and Older Juvenile Habitat and Movements
At dusk during sunmier and autumn seasons, age-i and older juveniles move shoreward into warmer water feeding areas where the young-of-the-year cod are concentrated. The attracting stimulus appears to be the periodic influxes of early settled cod (Keats 1990; Clark and Green 1990; Methven and Bajkik 1994). Age-1 cod have usually been found feeding until dawn primarily on mysids and ganimarid ampbipods; however, when they become about three times larger than settled age-0 juveniles, they begin cannibalizing the demersal 0-group cod (Grant and Brown i998a). By late fall, the earliest age-0 settlers may be large enough to begin intracohort cannibalism on the late settlers, as has been noted in waters of Iceland (Bogstad et al. 1994). When abundance of older juveniles is high, mortality may increase on young-of-the-year because of competition and predation from conspecifics (Grant and Brown 1998a). Age-1 cod have also been observed feeding on plankton after moving inshore in spring (Keats Ct al. 1987) as well as resting near bottom in shallow water at night (Keats and Steele 1992). In the latter situation, age-i were not feeding and analysis of stomach contents indicated daytime foraging on planktonic crustaceans leading the authors to speculate that post-transitional feeding on benthic invertebrates might be patchy in space and time. Where, when, and to some extent what yearlings eat is likely related to trade-offs between predation risk and food availability. -------------------------------------------------------- Inshore GOM HAPC page 7 Juvenile cod may utilize the intertidal zone for feeding purposes although there is no mention of this in recent studies. Earlier, an underwater television camera mounted on a herding fence recorded 423 "young" Atlantic cod (no size given), and Atlantic tomcod (Microgadus tomcod), which were sometimes indistinguishable from cod, as well as six, 3 0-40 cm (age-3 to 4) cod moving up and down a beach, either with or against tidal current, during daytime between June and October in Passamaquoddy Bay, New Brunswick (Tyler 1971). Of eight fish species observed undertaking these movements, the cod! tomcod combination ranked third, behind only winter flounder (Pseudopleuronectes amercianus) and Atlantic herring (Clupea harengus) in their use of the intertidal zone. Diel Dfferences in Abundance
Researchers studying young cod recognized that gear avoidance occurred during daylight, but avoidance was secondary to diel activity in explaining abundance differences between day and night catches for both age-0 and the older juveniles (Methven and Bajdik 1994; Gibson et al. 1996; Methven and Schneider 1998; Grant and Brown 1998b). Abundance of age-i peaked in the shore zone from August-November and again in April-June period, but was much reduced in winter (temperature <00C) indicating withdrawal to deeper habitat. The offshore movement by young cod was also reported in Passamaquoddy Bay, Bay of Fundy (MacDonald et al. 1984). ---------------------------------------------------------- Inshore GOM HAPC page 8 Sonic tagged age-3 cod (28-33 cm) rested almost exclusively in rocky areas at night during winter (Clark and Green 1990). Between June and September, however, individuals were active nocturnally and wide ranging (>3 km]day), moving daily between deep (30 m) cold water, where they were inactive in rocky areas, to shallow (<15 m) sandy substratum where they were active at night in relatively small feeding areas (~540-2,580 in2). When the water column became isothermal in September, age-3 cod remained in the shallow water during dayligtit leading researchers to speculate that the switch from nocturnal to diurnal feeding might be an antipredator strategy, i.e., to avoid being cannibalized at night when adult cod are seasonally active in relatively shallow water. Other common predators of juvenile cod off Newfoundland are pollock (Pollachius virens) and shortfinned squid (Jllex illecebrosus). Spatial Depth Gradient of Juveniles
The only coastal region of eastern Canada where the seasonal pattern of distribution for young cod appears to be different is the coastal portion of southern Gulf of St. Lawrence where water temperatures might be too warm during summer months (Hanson 1996). Fine scale distribution studies with trawls found that cod did not occupy water 2-12 m deep along shores of Pnnce Edward Island during summer. They were mostly absent from shallow waters (<20 m deep) in the Miramichi estuary and the contiguous Shediac Valley coastal shelf during any time of yeat. Yearlings and 2-year-olds, but not age-0 cod, were almost exclusively found in 15-35 m depths of the Gulf from June to early October before joining older age-groups in an extensive migration to deep (>100 m) offshore water for winter. The spatial depth gradient of juvenile cod from all other areas of eastern Canada seems consistent with published information from the Northeast Atlantic. The depth of highest age-0 cod abundance using a beam trawl off the British Isles was 6 m (Riley and Parnell 1984). Greatest density of age-i cod sampled with gill nets off Greenland was <20 m (Hansen and Lehmann 1986; Hovgard and Nygaard 1990). Acoustic surveys off the Norwegian coast showed most juveniles at depths <35 m and highest densities of demersal 0-group cod very close to rocky shores where the research vessel could not survey (Olsen and Soldal 1989). -------------------------------------------------------------------------------- Inshore GOM HAPC page 9 been observed in a number of cod stocks including the Labrador-East Newfoundland complex and southern Gulf of St. Lawrence stock. In the latter region, the area occupied by age groups 3-8+ cod increased as abundance increased (Swain and Wade 1993). In comparison to the older cod, age-3 were more spatially restricted at low population size, their range expanded more slowly as abundance increased, and changes in relative density among parts of the Gulf were smaller between years of low- and high-abundance. Younger juveniles were thought to experience less severe competitive pressures for food or wider variation in habitat quality than the older age-groups. A behavioral theory applied to explain the pattern of geographic distribution is density-dependent habitat use. This hypothesis was applied to young cod in coastal habitats (Olsen and Soldal 1989) where catches of post-settlement juveniles showed a high degree of small-scale spatial consistency regardless of cohort size. In years of high year-class abundance, density increases to an upper limit in the most suitable habitat and as the fitness of individuals occupying the prime sites declines due to intraspecific competition, diffusion to and use of suboptimal habitat expands. Accordingly, at low population size, individuals occupy habitat with high basic foraging and protective suitability. The theory was tested for the Labrador-East Newfoundland stock complex for which contraction has been confirmed for adult cod at low stock size (Taggart et al. 1994; Atkinson et al. 1997). Catches of age-groups 0-2 were analyzed from 1959-64 and 1992-94 at a series of fixed sampling sites extending over 1,500 miles of Newfoundland coastline (Schneider et al. 1997). In years of low cohort size, contraction did not occur in coastal habitats, i.e., density of juvenile cod was independent of area within the occupied <20 m depth range. They noted that sampling sites with high densities in some years had low densities in years of high abundance, an observation inconsistent with spillover theory in good years. In support of density-dependent theory, high post-settlement densities of age-0 cod were found in eelgrass beds of Trinity Bay, Newfoundland, during 1994 and 1995, years of good and bad year-classes, respectively; however, a significant increase in abundance in less suitable no-eelgrass habitat was noted in 1994 when settlement strength was high (Grant and Brown 1998a). The high 1994 densities in less-utilized no-eelgrass habitat during a year of high abundance would be consistent with the hypothesis of density-dependent habitat use or selection. The researchers acknowledged that their observations were on a small temporal and spatial scale. Re-analysis of the fixed sampling site juvenile catch data from Newfoundland showed a stronger recruitment signal from a small number of sites visited frequently than the entire set of sites (Lngs et al. 1997). The 1994 year class was ranked significantly stronger than the three previous year-classes following stock collapse in a broad-scale study (Anderson and Dalley 1997). On the other hand, there was no evidence of fewer settled 0-group juveniles anywhere along the coast in 1995 relative to the 1992-94 year-classes (Smedbol et al. 1998). For a number of cod stocks, variability in year class strength is usually determined in the larval
stage and attenuated by density-dependent juvenile mortality (Myers and Cadigan 1993a).
Biological processes that may result in density-dependent mortality would include:
------------------------------------------------ Inshore GOM HAPC page 10 circumscribed area of prime juvenile habitat with those settling surviving while others do not, resulting in a upper limit to the number of survivors regardless of egg/larval production. This mechanism could involve food limitation and/or increased predation risk outside a prime nursery area. It presumes mechanisms maintaining a relatively constant density such as territorial behavior or some other form of density-dependent habitat utilization. Notwithstanding the study by Schneider et al. (1997), many of the research results discovered and re-confirmed by scientists undertaking the studies summarized herein, describe or infer habitat mediated density-dependent mortality rates. These mechanisms systematically affect cod survival rates from the post-settlement pelagic stage well into the demersal juvenile stage. Annual variation in survival rates on these life stages may be more important in affecting year class size than survival in pre-settlement stages (Sissenwine 1984). This suggests that the nearshore bottom habitat may become a potential bottleneck to year-class size particularly in areas where the availability of the most suitable habitat might be low. Summary of Research
Inshore Gulf of Maine Activities ------------------------------------------------------- Inshore GOM HAPC page 11 The trade-offs between habitat use and frequency of feeding in the face of predation risk are processes consistent with density-dependent habitat use and mortality. Although empirical evidence of density-dependent usage off Newfoundland is contradictory, stock size/recruitment may not yet be large enough following the northern cod stock collapse to induce significant density-dependent effects on a large spatial scale. Nevertheless, behavioral research details ways age-O juveniles respond to spatial heterogeneity, the consequences for fitness through utilization of resources, and the intraspecific competitive effects which emphasizes the importance of habitat availability and quality in determining recruitment success. Gulf of Maine Coastal Marine Environment and Juvenile Cod Distribution Coastal Environment
From Cape Elizabeth to Cape Cod, the coast is characterized by long sandy beaches, unconsolidated cliffs and bluffs, and occasional rocky headlands, most prominently Cape Ann and Marblehead. With the exception of the headland littoral zone, the nearshore seafloor is generally wave-rippled coarse sand broken occasionally by restricted patches of cobble. Numerous barrier beaches protect estuaries and occasionally extensive salt marshes lying behind them. Along the southern part of the coast, in particular, but near entrances of protected inlets or river deltas, sand may be vegetated with eelgrass meadows. Sublittoral hard bottom relief including sand ripples, troughs, empty shells, worm tubes, motile or sessile invertebrate taxa (e.g., mussels, starfish, urchins, anemones, hydrozoans, bryozoans, ascidians, and sponges) and marine vegetation provides valuable interspersion of cover types for age-O juvenile nurser habitat similar to the nearshore regions of the Canadian maritime provinces. However, unhikç some areas north of the international border, the coastal zone is the only known source of recruits to the Gulf of Maine cod stock. -------------------------------------------------------------------- Inshore GOM HAPC page 12 The mapped EFH designations mirror the long held knowledge that inshore waters are principal habitat for juvenile cod. The distribution ofjuvenile cod observed in the latter half of 19th century and early part of this century was summarized by Bigelow and Schroeder (1953). They described young-of-the-year cod living in very shoal water to the littoral zone, and small, presumably one-year-olds, along the coast within two fathoms (~4 m) in summer. From the contemporary NMFS trawl survey catch in the Southern New England-Georges Bank region, water temperature was determined to be a factor in explaining interseasonal spatial and depth distribution of age-1-4 cod. However, water temperatures were insufficient to explain distributional differences among age classes (Wigley and Serchuk 1992). From a slightly earlier time series of research vessel catches in the Gulf of Maine, as well as collections on Georges Bank and Southern New England, Wigley and Gabriel (1991) noted juvenile (<37 cm) cod inhabiting a mean depth of 62 m in the spring and 75 m in the autumn with seasonal occurrence at minimum depths of about 9 m in both seasons. Within the Gulf of Maine, juvenile concentrations occurred between Jeffrey's Ledge and Cape Cod in spring and were more restricted to Massachusetts Bay in fall. Lower densities of juveniles also occurred all along the 100 m isobath off New Hampshire! Maine coast during both seasons. However, the NMFS survey completes relatively few stations nearshore in the northern part of the Gulf due to the rough bottom habitats that are untrawlable with traditional survey gear. .The most southern inshore portion of the Gulf of Maine is more accessible to research vessels and has been covered by the MDMF survey. The occurrence of juvenile cod (<35 cm) matched all temperatures (<130C) and depths sampled in spring (5-80 in), but during fall surveys, young cod tended to occur at deeper (15-50 m) and cooler (<170C) sampling stations. The juvenile cod catch per tow was highest along the north shore of Massachusetts Bay and Cape Ann! Ipswich Bay in spring (500-1,765 fish/tow) and fall (500-2,925 fish/tow), as well as the tip of Cape Cod in spring (200-500 fish/tow), and throughout Cape Cod Bay in fall (500-2,925 fish/tow) (NEFMC 1998). Age-groups 0 and 1 cod predominate in the fall survey with the highest densities of 0-group cod usually occurring at alongshore stations, catches invariably associated with bycatch of live bottom material [e.g., sulphur sponge (Cliona), kelp, spaghetti grass (Codium), and eelgrass (A. Howe, pers. comm.)]. Status of Eelgrass
-------------------------------------------------------------------------- Inshore GOM HAPC page 13 Because eelgrass is sensitive to variations in water quality from watershed-level impacts, it is considered an indicator of ecosystem state (Dennison et al. 1993). Whereas once large eelgrass meadows colonized much of the shallow water of Boston Harbor, they are now restricted to a few, small patches (Colarusso et al. in press). Airborne remote sensing, field observations, and GIS technology are being used to find and map eelgrass meadows in nearshore habitats of the Gulf of Maine. In comparison to other estuarine nursery habitats measured, species richness, macroinvertebrate biomass, and primary production is significantly higher in eelgrass. Its loss and subsequent changes in food web structure (McClelland and Valiela 1998) has not only resulted in foregone predator (benthic fish, lobster, and large shellfish) biomass (Heck et al. 1995), but also lost habitat complexity and diminished sediment stability. It is thought that some recolonization of former eelgrass meadows will occur slowly if nitrogen loading is reduced (Duarte 1995). Protecting eelgrass habitat should be an high priority with respect to conservation of coastal nurseries for Atlantic cod (Gotceitas et al. 1997). Utilization of Proposed HAPC by American Lobster and other Multispecies Groundfish The American lobster (Homarus americanus) is New England's largest single-species fishery and its most valuable. The life stage distribution relative to nearshore habitats of coastal lobster populations has been well documented. Densities tend to be at least two orders of magnitude higher on hard bottoms than on sediment habitat. Lobster larvae settle in shallow subtidal or low intertidal cobble! gravel! pebble substrates, and like post-settlement cod, are very susceptible to predation. These hard-bottom patches support high densities of one and two-year-olds (<40 mm CL) because of the protection afforded by the interstitial spaces (Wahle and Steneck 1992). No studies have detected early benthic stages (<10 mm CL) on featureless sediment (Wahle 1993). As lobsters outgrow the early benthic phase, they become increasingly mobile on nearshore sediment habitat. The research trawl catch of sublegal (3 0-82 mm CL) lobster alongshore at depths _9 m may reach 4,000 lobsters (13 bu) in tow times of less than 20 minutes in MDMF bottom trawl surveys (A. Howe, pers. comm.). Although Atlantic cod adults are depleted in the Gulf of Maine, some recruitment will continue to occur because density-dependent effects will increase juvenile survival rates at low abundance (Myers and Cadigan 1 993b). Unfortunately, recruitment at low spawner abundance happens at greatly reduced levels for cod (Myers and Barrowman 1996). Recognizing critical habitat (e.g., nearshore cobble patches and eelgrass beds), and protecting it from anthropogenic impacts by risk-adverse management measures should improve juvenile survivorship. ---------------------------------------------------------------- Inshore GOM HAPC page 14 Inshore Gulf of Maine HAPC Based on the information presented on juvenile Atlantic cod and the inshore areas of the Gulf of Maine, the EFH Technical Team suggests that the areas identified in this report and on Figure 1 meet the criteria for designation as an HAPC. A coastal L-IAPC designation would be justified on the criteria of ecological function and sensitivity to induced environmental degradation. An HAPC designation for the nearshore Gulf of Maine could assist in the enhancement of Atlantic cod, American lobster, and other groundfish species, such as winter flounder and white hake. Potential measures to protect this proposed HAPC are discussed below. The most practical approach for delineating an HAPC for settled age-0 cod is to circumscribe the reported center of distribution for this life stage throughout the range of the stock. The information available suggests that the HAPC should be from the low tide line to a depth of 9 m (30') MLW from eastern Maine to Cape Cod, Massachusetts, conforming to the center of distribution (4-7 in). This narrow depth range describes critical habitat from settlement (<5m) through the first autumn of life and overlaps seasonal babitat of age-i juvenile cod. It also bounds the critical nursery zone for early benthic stages of American lobster as well as important juvenile habitat for some other groundfish. Consideration of a more encompassing HAPC to the depth range occupied by most age-0 cod would involve extending the isobath to at least the 20 m (66') and might be unjustiflably exclusionary to mobile gear fisheries conducted on sandy seafloor seaward of hard bottom habitat and generally >10 m, should these gears be restricted with the proposed HAPC. The HAPC proposal should be somewhat flexible to allow modification as results from additional research and fine-scale resource mapping become available. For example, drawing a mean low water boundary of HAPC is problematic given knowledge that eelgrass beds may extend well inside embayments and river deltas, so drawing a shoreline boundary crossing from headland to headland versus across arbitrary points farther up estuary or river is initially convenient. Fine-scale mapping of most important habitat components might resolve the above dilemma and afford more localized protection to the most sensitive habitat components. It also could result in more permitted activities within the proposed HAPC zone. Future information could also prompt consideration of extending the HAPC into contiguous waters east of Cape Cod and south of Nantucket and Martha's Vineyard into Buzzards Bay. For assessment purposes, cod inhabiting this area are considered part of the Georges Bank stock. Settled age-0 cod are taken nearshore in May by the Massachusetts DMF trawl survey (NEFMC 1998). There is no information on whether or not these fish survive the summer. They do not re-occur at larger size on later inshore surveys but that does not mean that the southern shore zone does not serve an important role relative to recruitment for the Georges Bank stock. With consideration of the above caveats, the EFH Technical Team suggests that the Habitat Committee consider designating an HAPC for subtidal age-0 Atlantic cod, within the existing juvenile Atlantic cod EFH designation, from MLW to 9 in (30') below MLW extending from the international border with Canada southwestward along the entire western perimeter of the Gulf of Maine to Race Point, Provincetown, Massachusetts, including subtidal bottom to 9 m below MLW around all coastal islands. This designation could be refined at a later date, depending on ------------------------------------------------------- Inshore GOM HAPC page 15 the availability of better information about the actual distribution and spatial extent of seagrasses and hard bottom habitats. --------------------------------------------------------- New England Fishery Management Council Proposed Inshore Gulf of Maine Juvenile Atlantic Cod Habitat Area of Particular Concern --------------------------------------------------------- Inshore GOM HAPC page 17 Anderson, J.T. and E.L. Dailey. 1997. Spawning and year-class strength of northern cod (Gadus morhua) as measured by pelagic juvenile cod surveys, 1991-1994. Can. J. Fish. Aquat. Sd. 54(Suppl. 1): 158-167. Atkinson, D.B., Rose, G.A., Murphy, E.F., and C.A. Bishop. 1997. Distribution changes and abundance of northern cod (Gadus morhua), 1981-1993. Can. J. Fish. Aquat. Sci. 54(Suppl. 1):132-138. Brown, J.A., Pepin, P., Methven, D.A. and D.C. Somerton. 1989. The feeding, growth and behavior of juvenile cod, Gadus morhua L., in cold environments. J. Fish. Biol. 35:373-380. Bigelow, H.B. and W.C. Schroeder. 1953. Fishes of the Gulf of Maine. U.S. Fish Wildl. Serv., Fish. Bull. 53:1-577. Bogstad, B., Lilly, G.R., Mehl, S., Palsson, O.K., and G. Stefansson. 1994. Cannibalism and year-class strength in Atlantic cod (Gadus morhua) in Arcto-boreal ecosystem (Barents Sea, Iceland, and eastern Newfoundland. ICES Mar. Sci. Symp. 198:576-594. Campbell, J.S. 1997. Introduction to the Northwest Atlantic cod symposium. Can. J. Fish. Aquat. Sci. 54(Suppl. 1):1 Clark, D.S. and J.M. Green. 1990. Activity and movement patterns ofjuvenile Atlantic cod, Gadus morhua, in Conception Bay, Newfoundland as determined by sonic telemetry. Can. J. Zool. 68:1434-1442. Dailey, E.L. and J.T. Anderson. 1997. Age-dependent distribution of demersal juvenile Atlantic cod (Gadus morhua) in inshore! offshore northeast Newfoundland. Can. J. Fish. Aquat. 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Substrate selection by juvenile Atlantic cod (Gadus morhua): effects of predation risk. Oecologia 93:31-37. Gotceitas, V., Fraser, S. and l.A. Brown. 1995. Substrate selection by juvenile Atlantic cod in the presence of an actively foraging and non-foraging predator. Mar. Biol. 123:421-430. Gotceitas, V., Fraser, S. and l.A. Brown. 1997. Use of eelgrass (Zostera marina) by juvenile Atlantic cod (Gadus morhua). Can. J. Fish. Aquat. Sci. 54:1306-1319. Grant, S.M. and l.A. Brown. 1998a. Diel foraging cycles and interactions among juvenile Atlantic cod (Gadus morhua) at a nearshore site in Newfoundland. Can. J. Fish. Aquat. Sci. 55:1307-1316. ---------------------------------------------------- Inshore GOM HAPC page 18 Grant, S.M. and J.A. Brown. 1 998b. Nearshore settlement and localized populations of age-0 Atlantic cod (Gadus morhua) in shallow coastal waters of Newfoundland. Can. J. Fish. Aquat. Sci. 55:13 17-1327. Gregory, R.S. and J.T. Anderson. 1997. 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