796

COMMENT

THE POPULATION DENSITY OF MONSTERS IN LOCH NESS~

It is well known that there are monsters

in Loch

Ness. Their

most characteristic

features are that they are rarely seen and

never

caught,

but

there

are records

of

sightings

extending

back many centuries.

The fact that they are rarely

seen sug-

gests that the population

is small.

It is

known

from

direct

observation

that

the

animals

themselves

are large and it fol-

lows from this that the population

must

be small.

It can be demonstrated

quite

easily from trophic-dynamic

considerations

that many large animals could not exist in

Loch Ness; but a few could.

It has been

suggested from time to time that as the

monsters are never caught it must there-

fore follow

that they do not exist. This is

both irresponsible

and illogical.

Many

accounts

have been written

of

Loch Ness and its monsters (e.g. Holiday

1968) but very few quantitative

observa-

tions have been made. We know nothing

of their distribution.

The population

struc-

ture

of the monster

community

is also

unknown

to us. As they are rarely

seen

and never caught ( characteristic

features )

it is particularly

difficult

to study

their

population

dynamics.

However,

it is our

purpose to show that it is possible to esti-

mate the number

of monsters

that

can

exist in Loch Ness.

The

production

rate of oceanic

orga-

nisms is size dependent, but in ecologically

stable areas the standing stock is constant

at all sizes (Sheldon et al. 1972). It is not

unreasonable

to assume that similar

rela-

tionships

exist in large bodies of freshwa-

ter.

If this is so then the standing

stock

of monsters, taken over logarithmic

size

intervals, should be similar to that of other

organisms (e.g. fish or plankton).

We have not been able to find

any

information

on the standing stocks of Loch

Ness, but

an estimate

of the fish stock

can be made if

the probable

yield

is

known.

A deep oligotrophic

lake such as

1 Bedford

Institute

of Oceanography

Contribu-

tion.

Loch Ness should give an annual yield of

rather less than 1 kg ha-l yr-l.

This esti-

mate can be refined by calculations

based

on Ryder’s

(1964, 1965) morphoedaphic

index ( total dissolved solids/mean

depth ) .

Again, we could not find data from Loch

Ness and have used a value for total dis-

solved solids for the northern part of Loch

Lomond

(Darling

and Boyd 1969).

The

estimate of mean depth

was taken from

Hutchinson

( 1957).

By using this infor-

mation

in

Ryder’s

( 1964)

equation

wc

calculate

that Loch Ness should

give an

average fish yield

of 0.55 kg ha-l

yr-I.

The ratio of biomass to production

of a

fish

producing

system

will

range

from

about 1 to 5, so that the standing

stock

of fish in Loch

Ness should

lie in the

range from 0.55 to 2.75 kg ha-l.

The con-

centration

of monsters should be similar.

The area of Loch Ness is about 5,700 ha.

The total mass of monsters in the loch is

therefore in the range 3,135 to 15,675 kg.

In Fig. 1 we show the number of monsters

the loch could support relative

to individ-

ual size.

The minimum

average size is

taken

arbitrarily

as 100 kg;

anything

smaller

is not

suitably

monstrous.

The

number of monsters in the loch could vary

from 1 to 156 depending

on the standing

stock and average size. The largest num-

ber would

occur in the situation

where

high

standing

stock and

small

average

monster size coincide; however, we believe

that

such

a situation

is unlikely.

The

smallest number

must be more than two

if the species is to be maintained.

Mon-

sters have been seen in the loch for hun-

dreds of years so that there must be a

breeding

population.

The alternative

pos-

sibility,

a single monster of great age, is

unlikely,

and inter alia is not in keeping

with

the wide range of size estimates re-

ported in the literature.

A viable popula-

tion

could

be quite

small but probably

would not be less than 10. This constraint

is indicated

by the vertical

line in Fig. 1.

All the combinations

of individual

monster

weight

and population

shown by Fig.

1

COMMENT

797

are theoretically

possible, but we would

only

consider

those to the right

of the

vertical

line to be realistic.

We will now attempt to show that some

of the individual

monster weight

and pop-

ulation

combinations

are more probable

than

others.

Much

of our reasoning

is

based on observational

evidence.

The trophic

position

of the monsters is

probably

that of terminal

predators

feed-

ing on fish ( Holiday

1968).

The growth

efficiency

of many

aquatic

predators

is

around 10%. If the monsters are similarly

efficient

and if a major part of the fish

production

is used by them, then their

production

must be of the order of 300

kg yr-l

or more. The average number

of

deaths per year is determined

in a stable

population

by the ratio of production

to

mean size. On this basis monsters weigh-

ing 100 kg would

have to die at a mini-

mum rate of about 3 per year.

Larger

monsters would

die less frequently.

Two lines of evidence support the view

that monsters do not die frequently

and

must therefore

be large.

Firstly,

corpses

are never

found.

Secondly,

a relatively

large number

of juveniles

must exist if

adult mortality

is high, but although

small

monsters have been seen from time to time

they are not common.

It seems therefore

that Loch Ness must contain a small num-

ber of large monsters.

These could weigh

as much as 1,500 kg with a population

of

lo-20

individuals,

A

1,500-kg

monster

could be about 8 m long, a size that agrees

well with

observational

data.

We are aware that in these calculations

we have not taken migratory

fish into con-

sideration

These will

increase the effec-

tive standing

stock of the loch and this

could

result

in there being

either

more

or larger monsters than we have shown.

However,

Sheldon

et al. (1972)

suggest

that

standing

stocks are not

absolutely

constant.

There is probably

some decrease

at the higher

trophic

levels which

could

result

in

there

being

either

fewer

or

smaller

monsters

than

we have

shown.

These two factors are antipathetic,

and al-

though we do not know the relative

mag-

100

Total

Population

FIG.

1.

The

probable

number

of monsters

in

Loch

Ness.

Upper

curve:

at a standing

stock of

2.75 kg ha-‘;

lower

curve:

at a standing

stock of

0.55 kg ha-l.

The vertical

line indicates

the sug-

gested minimum

population

size.

nitudes, they are both likely

to be of the

order of a factor of two.

They will

tend

to cancel each other and it is not improb-

able therefore

that the population

density

that we have described- for the monsters

in Loch Ness is near to the true value.

It is not unknown

for sightings

of mon-

sters, both in Loch Ness and elsewhere, to

go unrecorded

(Heuvelmans

1968; Holiday

1968). Fear of ridicule

is the main reason

why

many observers do not make their

observations

known

to science.

But it is

the skeptics who

are at fault.

Monster

observers should be encouraged.

The oc-

currence

of monsters is quite

reasonable

and is by no means fantastic.

We would

like to thank

Kate Kranck

for drawing

our attention

to this problem,

because until

she mentioned

it we were

unaware that monsters were a problem.

R. W.

SHELDON

S. R. KERR:!

Fisheries Research Board of Canada,

hlarine

Ecology

Laboratory,

Bedford Institute

of Oceanography,

Dartmouth,

Noz;a Scotia.

3 Present

address:

Ministry

of

Natural

Re-

sources,

Research

Branch,

Maple,

Ontario.

798

COMMENT

REFERENCES

DARLING,

F. F.,

AND

J. M.

BOYD.

1969.

The

highlands

and islands.

Collins.

405 p.

HEWELMANS,

B.

1968.

In the wake

of the sea-

serpents.

Rupert

Hart-Davis.

645 p.

HOLIDAY,

F. W.

1968.

The

great omr of Loch

Ness.

Faber

and Faber.

223 p.

HUTCHINSON,

G. E.

1957.

A treatise

on lim-

nology,

v. 1.

Wiley.

1015 p.

RYDER, R. A.

1964.

Chemical

characteristics

of

Ontario

lakes,

with

reference

to

a method

for estimating

fish production.

Ontario

Dep.

Lands

Forests.

Sect. Rep.

(Fish.)

48. 75 p.

-.

1965.

A

method

for

estimating

the

potential

fish

production

of north-temperate

lakes.

Trans.

Amer.

Fish. Sot. 94:

214-218.

SHELDON,

R. W., A. &AKASH,

ASD

w.

H. SUT-

CLIFFE,

JR.

1972.

The

size distribution

of

particles

in the

ocean.

Limnol.

Oceanogr.

17: 327-340.

1. The vertical and horizontal distribution of phytoplankton, zooplankton and fish in Loch Ness, Scotland, were monitored during one day-time and one night-time survey in July 1992. The vertical samples were collected at a site located at the northern end of the loch and the horizontal samples along a longitudinal transect.2. The vertical distribution surveys demonstrated that the phytoplankton, the zooplankton and the fish were concentrated in the top 30 m of water above the seasonal thermocline. Within this layer, Cyclops stayed much closer to the surface than Eudiaptomus but both species moved towards the surface at night.3. The most important factor influencing the horizontal distribution of the phytoplankton was the north–south gradient in productivity. The sub-catchments surrounding the north basin contain a greater proportion of arable land than those to the south and the concentrations of nitrate-nitrogen and phytoplankton chlorophyll increased systematically from south to north.4. Zooplankton distribution patterns were influenced by wind-induced water movements and the dispersion of allochthonous material from the main inflows. The highest concentrations of Cyclops were recorded in the north, where there was more phytoplankton, and the highest concentrations of Eudiaptomus in the south, where there were higher concentrations of non-algal particulates.5. There was no spatial correlation between total zooplankton and total fish abundance but the highest concentrations of small (1–5 cm) fish were recorded in the south where there was a large patch of Eudiaptomus. The number of Eudiaptomus at specific locations within this patch were, however, negatively correlated with the numbers of small fish. These results suggest that the fish were actively foraging within the patch and were depleting their zooplankton prey in the areas where they were most abundant.

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... The hypothesis states that, in the epilimnion of stratified lakes, the surface wind current carries the organisms located there to the shore where the wind blows (leeward shore), and the compensatory current in the lower layers of the epilimnion (suprathermocline current) carries the organisms to the opposite one, from where the wind blows (windward shore). The combination of wind currents, vertical migration of organisms, and internal wave movements leads to large-scale redistributions of zooplankton (George and Winfield, 2000;Blukacz et al., 2009) and phytoplankton (Moreno-Ostos et al., 2009;Mackay et al., 2011;Reichwaldt et al., 2013;Cyr, 2017;Mineeva, 2021), and it can also affect the functioning of the entire trophic system of the reservoir (Rinke et al., 2009;de Kerckhove et al., 2015). Abiotic factors (wind currents, temperature, and illumination) usu-ally determine macroscale plankton heterogeneities, while biotic factors (predator pressure and the uneven distribution of food resources) determine microscale ones (Pinel-Alloul, 1995;Benoit-Bird et al., 2009;Rinke et al., 2009). ...

... These data confirmed the existence of a pronounced horizontal heterogeneity in the distribution of planktonic organisms in Lake Shira and testified in favor of the stated hypothesis of the formation of horizontal inhomogeneities under the action of layer-by-layer wind currents of the epilimnion. Indeed, the northeast wind in the daytime contributed to the transfer of surface water depleted in zooplankton to the southwestern (leeward) shore and the displacement of zooplankton in the direction of the northeastern (windward) shore, similarly to the transfer of сalanoids by wind currents in Lake Loch Ness (George and Winfield, 2000). As for phytoplankton, positively buoyant algae occupying the upper layer of the epilimnion (first and foremost, blue-green and green) are moved to the leeward coast (Moreno-Ostos et al., 2009;Mackay et al., 2011;Reichwaldt et al., 2013;Mineeva, 2021), i.e., in our case, to the south one. ...

... The spatial heterogeneity of zooplankton on a scale of 5-6 km (and inside it of 0.5-2 km) was found even in small mountain lakes, where the influence of wind is theoretically reduced only to internal waves and small-scale Langmuir circulation (Urmy and Warren, 2019). In some cases, wind causes a heterogeneous spatial distribution of only zooplankton, while phytoplankton heterogeneity is caused by uneven nutrient loading and catchment use (George and Winfield, 2000). ...

A hypothesis about the formation of horizontal heterogeneities of zooplankton and phytoplankton for the lake subjected to regular daily changes in wind currents has been tested. Formation of horizontal heterogeneities is based on a combination of low-amplitude vertical migration of zooplankton and epilimnion wind currents: surface currents, which bring water depleted in zooplankton to the downwind shore (in the direction in which the wind is blowing), and compensatory above-thermocline ones, which bring zooplankton-enriched water to the upwind shore (against the wind). The spatial separation of phytoplankton and zooplankton may result in the weakening of trophic links between these trophic levels. The hypothesis was tested in 2020 in the pelagic zone of Lake Shira (Khakassia, Russia), a brackish meromictic water body with simple bathymetry and a simple food web. The epilimnion horizontal heterogeneities were assessed using a survey across the lake by measuring biological and physical parameters with a submersible fluorimeter probe and a plankton net at 11 stations and recording the dynamics of wind speed and direction. Differences in the values of primary production, plankton destruction, and intensity of phytoplankton grazing by zooplankton near the downwind and upwind shores were estimated using the bottle method in 3 experiments. The experiments confirmed the expected differences in the functioning of the trophic cascade near the northeastern (more often upwind during the day and downwind at night) and south-southwestern (downwind during the day and upwind at night) shores. Namely, the concentration of chlorophyll a, the gross and net primary production of phytoplankton (estimated by bottle and fluorescent methods), and the daily intensity of zooplankton feeding (based on chlorophyll) were higher near the southern coast, while the biomass of net zooplankton and the respiration rate of the plankton community were higher near the northeastern shore, which coincided with the pattern of phyto- and zooplankton distribution over the lake according to the sampling data under similar weather conditions. The hypothesis was confirmed and supplemented by the data on the evening-night vertical migrations of zooplankton.

... The hypothesis states that, in the epilimnion of stratified lakes, the surface wind current carries the organisms located there to the shore where the wind blows (leeward shore), and the compensatory current in the lower layers of the epilimnion (suprathermocline current) carries the organisms to the opposite one, from where the wind blows (windward shore). The combination of wind currents, vertical migration of organisms, and internal wave movements leads to large-scale redistributions of zooplankton (George and Winfield, 2000;Blukacz et al., 2009) and phytoplankton (Moreno-Ostos et al., 2009;Mackay et al., 2011;Reichwaldt et al., 2013;Cyr, 2017;Mineeva, 2021), and it can also affect the functioning of the entire trophic system of the reservoir (Rinke et al., 2009;de Kerckhove et al., 2015). Abiotic factors (wind currents, temperature, and illumination) usu-ally determine macroscale plankton heterogeneities, while biotic factors (predator pressure and the uneven distribution of food resources) determine microscale ones (Pinel-Alloul, 1995;Benoit-Bird et al., 2009;Rinke et al., 2009). ...

... These data confirmed the existence of a pronounced horizontal heterogeneity in the distribution of planktonic organisms in Lake Shira and testified in favor of the stated hypothesis of the formation of horizontal inhomogeneities under the action of layer-by-layer wind currents of the epilimnion. Indeed, the northeast wind in the daytime contributed to the transfer of surface water depleted in zooplankton to the southwestern (leeward) shore and the displacement of zooplankton in the direction of the northeastern (windward) shore, similarly to the transfer of сalanoids by wind currents in Lake Loch Ness (George and Winfield, 2000). As for phytoplankton, positively buoyant algae occupying the upper layer of the epilimnion (first and foremost, blue-green and green) are moved to the leeward coast (Moreno-Ostos et al., 2009;Mackay et al., 2011;Reichwaldt et al., 2013;Mineeva, 2021), i.e., in our case, to the south one. ...

... The spatial heterogeneity of zooplankton on a scale of 5-6 km (and inside it of 0.5-2 km) was found even in small mountain lakes, where the influence of wind is theoretically reduced only to internal waves and small-scale Langmuir circulation (Urmy and Warren, 2019). In some cases, wind causes a heterogeneous spatial distribution of only zooplankton, while phytoplankton heterogeneity is caused by uneven nutrient loading and catchment use (George and Winfield, 2000). ...

... Mild steady winds have been shown to concentrate buoyant phytoplankton at the downwind end of the lake, but these aggregations are broken down and the algae are homogenised through the surface mixed layer at wind speeds above c. 4 m/s (George & Edwards, 1976;Reynolds et al., 1987;Small, 1963). Zooplankton also position themselves vertically in response to environmental cues, such as light, temperature, dissolved oxygen, food, and predators (Hansson & Hylander, 2009;Jensen et al., 2001), and are accumulated downwind (or upwind) by wind-driven currents (Blukacz et al., 2009;George & Edwards, 1976;George & Winfield, 2000). The capacity of different planktonic organisms to maintain (or not) their vertical position affects the speed at which they are transported and the degree to which they are aggregated by surrounding hydrodynamic forces (Cyr, 2017;Garwood et al., 2020;Reynolds et al., 1987). ...

... The capacity of different planktonic organisms to maintain (or not) their vertical position affects the speed at which they are transported and the degree to which they are aggregated by surrounding hydrodynamic forces (Cyr, 2017;Garwood et al., 2020;Reynolds et al., 1987). Effects of wind-driven forces vary among zooplankton taxa (George & Edwards, 1976;George & Winfield, 2000) and with body size (Blukacz et al., 2009; W.G. ...

... Our basin-wide data support the hypothesis that zooplankton biomass accumulates downwind with increasing wind speed, but this relationship was only observed in small-bodied zooplankton (≤507 μm ECD) and the magnitude of the downwind accumulation was modest, with only 10%-50% higher biomass downwind compared to upwind sites. The conveyor-belt model (George & Edwards, 1976;Rueda & Vidal, 2009) predicts downwind accumulation of buoyant phytoplankton and of zooplankton that are strong enough swimmers to avoid being entrained in a return current, and is commonly used to explain basin-scale plankton distributions (George & Winfield, 2000;Lacroix & Lescher-Moutoué, 1995;Thackeray et al., 2004;Vidal et al., 2014). Contrary to predictions from the conveyor-belt model, we found that small zooplankton accumulated at the downwind end in South Arm on windy days, but the basin-wide distribution of large zooplankton, which tend TA B L E 3 Best general additive mixed models describing the relationships between dependent zooplankton distribution variables (STDBIOM, ΔBIOM, CV) and independent variables: wind speed (WS); zooplankton body size (SIZE: 1 = small zooplankton, 2 = large zooplankton; SmZ is small zooplankton, LgZ is large zooplankton); transect position in the basin relative to wind (BASIN: 0 = upwind, 1 = downwind; Upwind, Downwind); and transect position relative to shore (SHORE: 0 = offshore, 1 = inshore; Offshore, Inshore) ...

• William Gary Sprules
• Hélène Cyr

Wind‐driven forces are expected to concentrate zooplankton along downwind shores in lakes and provide food subsidy to nearshore food webs, but the bathymetric complexity of nearshore areas could result in high spatial variability. Here we test: (1) whether zooplankton accumulate downwind on windy days, and whether the magnitude of accumulation varies with zooplankton body size and with nearshore bathymetric slope; and (2) whether nearshore zooplankton are more spatially variable than offshore zooplankton, and whether their spatial variability is related to wind conditions and to zooplankton body size. This study focuses on zooplankton distribution at the whole‐lake basin and at intermediate (10 m–1 km) spatial scales. Zooplankton were sampled repeatedly along four c . 1 km transects at each of the upwind and downwind ends of a 22.1‐km ² stratified lake basin. Two transects were oriented perpendicular to shore and two were parallel, one close to shore and the other further offshore. Zooplankton were sampled along each transect using an optical plankton counter morning and afternoon over 3 consecutive days, under a range of wind conditions, during early stratification (early June), mid‐stratification (mid‐July) and late stratification (late September). A 3D‐hydrodynamic model was used to help interpret the results. Small‐bodied zooplankton accumulated downwind during windy periods, reaching 8%–34% higher biomass than the basin‐wide average. This downwind accumulation of biomass was best explained by a partial (metalimnetic) upwelling displacing the epilimnion to the downwind end of the lake basin. Active upward movement of zooplankton is required to explain near‐surface biomass accumulation in this displaced water mass. Large‐bodied zooplankton accumulated in nearshore areas, regardless of wind conditions. Higher nearshore accumulation of large zooplankton was observed along transects following a shallow (1.9%) bathymetric slope but not along a steep (6%) slope. Large‐bodied zooplankton are more patchily distributed than small‐bodied zooplankton, both nearshore and offshore. The spatial variability of large zooplankton declined with increasing wind speed, but only at upwind sites. The patchy distribution of large‐bodied zooplankton is driven, or at least strongly influenced, by biological processes. The spatial distribution and patchiness of zooplankton varies with wind speed, zooplankton body size and nearshore bathymetry. Planktonic organisms are not passive drifters , and their patchiness and influx to certain parts of the lake during windy periods are both expected to affect the efficiency of trophic transfers in lake food webs.

... However, there is increasing evidence of marked spatial variation in the zooplankton and other potential prey of the pelagic zones of lakes (e.g. George & Edwards 1976, Betsill & Van Den Avyle 1994, Pinel-Alloul 1995, George & Winfield 2000, which is the most important habitat inhabited by Arctic charr in most areas of its distribution. The implications of such variation for fish diet composition have been little studied and an investigation of the diet of roach, Rutilus rutilus L., among contrasting basins of an oligotrophic lake in Spain by Garcia-Berthou (1999) is a notable exception. ...

... The fish community of Loch Ness is dominated by Arctic charr and the loch's pelagic zone comprises a single, simple elongate basin, making it an ideal site for the study of within-habitat spatial variation in the diet of this species. Moreover, a number of studies (Kubecka et al. 1993, Shine et al. 1993, Jones et al. 1995, George & Winfield 2000 have examined spatial variations in physical features, nutrients, phytoplankton, zooplankton and fish within the pelagic zone of this loch, providing an excellent background for the interpretation of a corresponding diet study of Arctic charr. These investigations have shown that although catchment influences exert an effect on the distribution of nutrients and hence phytoplankton, these and higher trophic levels are also susceptible to windinduced currents and counter-currents along the elongate southwest-northeast axis. ...

... While in other lakes such prey are obtained from benthic or profundal habitats, in Loch Ness they are obtained from the pelagic zone. This unusual conclusion is supported by the observations at Loch Ness that Arctic charr are largely restricted to the epilimnion and show no diel inshore or descending migrations (Kubecka et al. 1993, Shine et al. 1993, George & Winfield 2000, and that chironomid larvae and pupae are persistently present in the epilimnion (Shine et al. 1993). ...

• Ian J. Winfield
• Colin W Bean
• D. P. Hewitt

The pelagic fish community of Loch Ness, U.K., is dominated by Arctic charr, Salvelinus alpinus. Previous studies have shown that the distribution of zooplankton along the south-west to north-east axis of this elongate loch is very dynamic and determined largely by prevailing winds, but Arctic charr are consistently more abundant in the southern half of the loch. In July 1993, the diet compositions of 161 Arctic charr from 53 to 330 mm in length were determined and related to their spatial distribution and those of microcrustacean zooplankton and pelagic chironomid larvae and pupae. Diets were dominated by chironomid larvae, with chironomid pupae, Bythotrephes longimanus, Bosmina coregoni and Daphnia hyalina also frequently taken. Over the whole study period, B. longimanus were more important in the diet of fish from the northern half of the loch, while chironomid larvae were more important for fish from the southern half. As a result, per capita prey weight of fish from the south was greater than that of fish from the north. However, wind-induced changes in the distribution of zooplankton along the loch were accompanied by a change in the diet composition of Arctic charr from the south.

... However, past research has focused on spatial variability in plankton. This previous research indicates that summer zooplankton abundance and assemblage composition can be heteroge-neous across space within the Great Lakes, especially in coastal areas during the summer months (Watson andWilson 1978, Kwiatkowski 1980) and can be caused by winddriven surface currents (George and Winfield 2000). Previous research comparing abundances across depths in Lake Michigan indicates that zooplankton are most abundant at mid-depth sites (20-to 45-m depth;Evans et al. 1980, Pothoven andFahnenstiel 2015), so zooplankton density could also be affected by movement of water from middepth to coastal areas. ...

... Fish were more abundant early in the summer in 2015 than in 2016. Planktivorous fish can reduce zooplankton densities at local scales (Kalikhman et al. 1992, George andWinfield 2000), so it is possible that fish reduced zooplankton abundance early in the summer in 2015. Temperature was associated with fish abundance and assemblage composition in coastal areas, and as temperatures increased the abundance of Round Gobies increased and that of Lake Whitefish, Shiners, and Brook Stickleback decreased. ...

摘要

本研究探讨了尼斯湖怪物的种群密度问题。作者通过营养动态学考量，证明尼斯湖虽不能支持大量大型生物，但可以维持少量大型生物的生存。研究基于稳定生态系统中不同大小生物的存量应相似的假设，通过估算尼斯湖的鱼类资源量来推断可能的怪物数量。

根据Ryder的形态营养指数计算，尼斯湖的年均鱼类产量约为0.55千克/公顷/年，鱼类存量估计在0.55-2.75千克/公顷之间。尼斯湖面积约5,700公顷，因此湖中怪物的总质量应在3,135-15,675千克范围内。

作者认为，如果怪物平均体重为100千克（最小合理体型），湖中怪物数量可能在1-156只之间，但考虑到繁殖需求，可行种群不应少于10只。基于怪物尸体从未被发现且幼体较少见的观察证据，作者推断尼斯湖可能存在10-20只大型怪物，每只重约1,500千克，长约8米，这与目击报告相符。研究表明，尼斯湖怪物的存在从生态学角度是合理的。

与问题相关的信息提取

根据这篇研究，尼斯湖的鱼类资源量和生态系统支持大型掠食动物的能力可以从以下几个方面分析：

1. 鱼类资源量估计：

   • 尼斯湖作为深水贫营养湖泊，年鱼类产量估计约为0.55千克/公顷/年（基于Ryder的形态营养指数计算）
   • 鱼类生物量与产量比例在1到5之间，因此尼斯湖的鱼类存量估计在0.55-2.75千克/公顷之间
   • 尼斯湖面积约5,700公顷，总鱼类生物量估计在3,135-15,675千克范围内

2. 生态系统支持大型掠食动物的能力：

   • 研究明确指出："可以通过营养动态学考量轻松证明，尼斯湖不能支持许多大型动物；但可以支持少量大型动物"
   • 如果大型掠食动物（研究中称为"怪物"）作为终端捕食者以鱼类为食，其生长效率约为10%
   • 假设这些掠食动物消耗大部分鱼类产量，则它们的年产量约为300千克或更多
   • 研究表明湖中可能存在10-20只大型掠食动物，每只重约1,500千克，长约8米

3. 生态系统平衡因素：

   • 研究考虑了两个相反的因素：洄游鱼类可能增加有效存量，而较高营养级别的存量可能有所减少
   • 这两个因素相互抵消，各自影响可能是两倍左右的变化
   • 作者认为最终计算的种群密度接近真实值

总结来看，尼斯湖的鱼类资源量相对有限（约3,135-15,675千克），但其生态系统确实能够支持少量大型掠食动物的生存，这些掠食动物可能形成一个小型但可行的种群（10-20只），作为终端捕食者在生态系统中占据一席之地。

相关网页链接

网页中未包含可点击的网页链接。

相关图片

图片1:

• title: 尼斯湖怪物可能数量图表
• content: 显示了尼斯湖中怪物可能数量与个体重量的关系曲线。上曲线表示存量为2.75千克/公顷时的情况，下曲线表示存量为0.55千克/公顷时的情况。垂直线表示建议的最小种群规模。
• source: R. W. SHELDON 和 S. R. KERR
• link: 图1（Fig. 1）

摘要

这篇研究对尼斯湖（Loch Ness）的浮游生物和鱼类分布进行了全面调查。研究在1992年7月进行了一次白天和一次夜间的监测，采样点位于湖的北端和纵向断面。研究发现浮游植物、浮游动物和鱼类主要集中在季节性温跃层以上的30米水层内。在这一水层中，剑水蚤（Cyclops）比真剑水蚤（Eudiaptomus）更靠近表面，但两种生物在夜间都会向表面移动。浮游植物的水平分布主要受南北生产力梯度影响，北部盆地周围的子流域含有更多可耕地，导致硝酸盐氮和浮游植物叶绿素浓度从南向北系统性增加。浮游动物的分布受风引起的水流运动和主要入流处的异源物质扩散影响。剑水蚤在浮游植物更丰富的北部浓度最高，而真剑水蚤在非藻类颗粒浓度更高的南部浓度最高。研究未发现浮游动物总量与鱼类总丰度之间的空间相关性，但小型鱼类（1-5厘米）的最高浓度出现在南部，与真剑水蚤大量聚集的区域重合，表明鱼类在这些区域积极觅食，减少了浮游动物数量。

与尼斯湖鱼类群落相关的信息

根据网页内容，关于尼斯湖的鱼类群落和资源量，可以提取以下关键信息：

1. 鱼类垂直分布：尼斯湖的鱼类主要集中在季节性温跃层以上的30米水层内。这表明尼斯湖的鱼类主要活动在上层水域，而非深水区域。

2. 鱼类与浮游动物的关系：研究发现鱼类总丰度与浮游动物总量之间没有明显的空间相关性，表明鱼类分布可能受到多种因素影响，不仅仅是食物资源。

3. 小型鱼类的分布特征：小型鱼类（1-5厘米）主要集中在尼斯湖南部区域，这些区域恰好是真剑水蚤（Eudiaptomus）大量聚集的地方。

4. 捕食关系的证据：在真剑水蚤密集区域内，真剑水蚤的数量与小型鱼类数量呈负相关，这表明鱼类在这些区域积极觅食，导致浮游动物数量减少。这一发现证实了鱼类对其猎物浮游动物的捕食压力。

5. 鱼类资源量：虽然网页内容没有直接提供尼斯湖鱼类资源量的具体数据（如总生物量或密度），但研究表明鱼类分布不均匀，主要集中在特定区域（如南部的浮游动物丰富区）。

6. 生态系统功能：研究结果表明尼斯湖的鱼类在生态系统中扮演着重要的捕食者角色，通过捕食浮游动物来调节水生生态系统的结构。

总体而言，这项研究揭示了尼斯湖鱼类群落的空间分布特征及其与浮游动物之间的相互作用关系，但没有提供具体的鱼类资源量数据。研究表明尼斯湖的鱼类主要是小型鱼类，集中在上层水域，并且在食物丰富的区域形成了明显的捕食压力。

相关网页链接

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1. 标题: Publication PDF Icon
   内容: 研究论文PDF图标
   来源: ResearchGate
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