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120 years of change in fishing powerof English North Sea trawlers

Georg H. Engelhard23 April 2008

A seminar celebrating the launch of

Anecdote: the ‘sailing smack’ experiment• 1990s Cefas scientists

boarded sailing smack Excelsior and fished off Lowestoft for a week

• Aim: compare current with ‘virgin’ state of North Sea, using fishing methods of 120 years ago—beam trawling by sail

• 1880s sailing trawlers were responsible for ~100,000 tonnes fish landed in UK

Results of the ‘sailing smack’ experiment

• Lack of skills by scientists and crew (despite hard labour)?

• Has North Sea become so scarce of fish resources?

Few dab and dragonet, otherwise near-zero catch—WHY?

Lack of fishing power? Lack of fish?

Fishing power

• Expresses differences in cpue between fishing vessels if fishing at same time and location

• General trend of increasing fishing power over time• Typically, fishing power studies limited to 1–2

decades• What about long-term trends?

How has fishing power changed over 120 years of trawling the North Sea?

Overview‘Time travel’ through 5 “fishing power ERAS”

1. 1400s–1890s Sail to early steam trawlers

2. 1900s–50s Golden Age steam trawlers

3. 1950s–60s Steam gives way to diesel

4. 1960s–80s Rise of modern beam trawlers

5. 1980s–now Recent changes fishing power

Era 1. 1400s–1890sFrom sailing to early steam trawling

Origin of trawl

• 14th Century, Thames: “wondyrchoun” — primitive beam trawl

• Already hated by other fishermen

Michael Graham (1956): “Opposition against the trawl has continued throughout history, but never halted its development.”

Trawling taken to open sea• Historians disagree; 3 views:

-6 -4 -2 0 2 4

5052

54

Barking (Thames)

Brixham (Devon)

Dutch coast

1821

19th Century expansion trawling North Sea• Quick spread

throughout North Sea• Causes:

– Industrial revolution– Population growth,

demand and markets– Railway allowing fast

transport fresh fish from port to market

First ‘leap’ in fishing power

• Trawling by sail peaked in 1870s, then declined

• Decline caused by first major jump in fishing power — introduction of steam

Advantages of steam trawlers• Not subject to mercies of wind• Range further from port• Trawl faster and deeper• High trawl speed allowed switch from beam to

otter trawl• Iron, later steel hulls• Garstang (1900):

– 1881: first steam beam trawlers had 4x higher fishing power than sailing beam trawlers

– 1898: steam otter trawlers already had 8x higher fishing power

Era 2. 1900s–1950sGolden Age of steam trawling

Great Yarmouth, 1930s

Rise, rule, and decline of steam trawling

Turn of century: steam trawlers built rapidly

1890s-1950s: ‘Golden Age’, steam trawlers landed 50-80% of North Sea demersal landings UK

Both World Wars: significant reductions effort, but steam trawling quickly recovered afterwards

Extensiveness of steam trawling• 1900s-1950s: British steam trawlers

fished throughout North Sea• More extensive spatial distribution than

British fisheries nowadays• British steam trawlers caught 25-70% of

international North Sea demersal catch

• Sailing trawlers only survived until 1930s, in IVc

• Co-occurrence allowed fishing power comparison

Fishing power of steam trawlersexpressed in ‘sailing smack units’

Steam trawlers, fishing in the same rectangle at the same time as sailing trawlers, had...

...about 4x higher plaice fishing power...

...about 10-20x higher cod fishing power!

Era 3. 1950s–1960sSteam giving way to diesel

Post-WWII decades• Steam trawl fleet now mainly old vessels—fishing

power probably equal to pre-WWII– during war, best trawlers requisitioned by Navy as

minesweepers, and many destroyed

• Change within steam trawlers: from coal burners to oil burners (but still driven by steam)

• Could not halt decline steam trawlers: competition with motor trawlers– had already existed from WWI, but only as sailing

trawlers with small petrol/paraffin motors installed– 1946: first purpose-built diesel-driven motor trawler

Fishing power of motor (diesel) trawlersexpressed in ‘steam trawler units’

...about equal cod fishing power and...

...only marginally higher plaice fishing power, but...

1950s–1960s motor trawlers, fishing in the same rectangle at the same time as steam trawlers, had...

...this was despite far greater average tonnage of steam trawlers!

1950s and 1960s: large steam trawlers were gradually outcompeted by on average smaller but equally or increasingly efficient motor trawlers

Trends in North Sea fishing effortin British sailing, steam and motor trawlers

Era 4. 1960s–1980sRise of modern beam trawlers

Rise of modern (twin) beam trawlers• Two large beam trawls lowered mechanically from

side of ship, often with tickler chains, very effective for catching sole and plaice

• Developed by Dutch and Belgian fisheries in 1960s

• UK slow to follow in North Sea—only in 1980s• UK beam trawling peaked 1990s, then declined,

and now almost gone from North Sea (but strong in SW)

• However, international effort in North Sea high, arguably most invasive fishing method here

Rise of Netherlands beam trawl fleet

Strong 1963 year-class leads to Dutch ‘wave’ of new large beam trawlers rapidly built

Note decrease mean tonnage English otter trawlers in southern North Sea

First success Dutch beam trawlers linked to strong 1958 sole year-class

Fishing power of Dutch beam trawlers

...initially ~2x, later ~8x higher plaice fishing power...

...initially lower, later on ~equal cod fishing power...

1960s–1970s: Dutch beam trawlers, compared to English otter trawlers fishing in IVc, had...

...but were actually targeting sole

Era 5. 1980s–nowRecent changes fishing power

RV Corystes, 2004

1980s–present: recent changes fishing power

• From 1977 on, we have consistent North Sea survey data: IBTS, EGFS

• Compared fishing power English commercial otter and beam trawlers, with that of EGFS

• Based on commercial and survey cpue in same rectangles, same month

Fishing power of commercial otter trawlers expressed in ‘EGFS units’

Compared to EGFS survey, commercial otter trawlers...

...in 1980s have ~5–10x higher, later only ~1–3x higher plaice fishing power...

...and in most years about equal cod fishing power as the EGFS (but in some years ~3–6x higher).

Fishing power of commercial beam trawlers expressed in ‘EGFS units’

...in most years, have roughly half the cod fishing power...

Compared to EGFS survey, commercial beam trawlers...

...and have decreasing, but always far higher (~20–50x!) plaice fishing power, confirming efficiency beam trawl for flatfish

Conclusions

• Past 120 years: fishing power has increased substantially

• Trend has not been gradual: – FP has sometimes “leapt forward” in few years– FP has also “stagnated” for decades

• Combined all estimated FP changes: – Estimated total change over 120 years (plaice

and cod)

Total change fishing power over 120 years

...beam trawlers in 2000 have ~10x higher cod FP and ~100x higher plaice FP...

Compared to 1880s sailing beam trawlers...

...otter trawlers in 2005 have ~50x higher cod FP and ~4x higher plaice FP...

However, fisheries have not necessarily become more profitable!

Comparison historical and modern plaice cpue and fishing power

Rijnsdorp & Millner (1996): North Sea plaice was about equally abundant in 1920s and ~2000

Comparison historical and modern plaice cpue and fishing power

Modern beam trawlers have 100x higher FP than 1920s sailing trawlers, but only 5x higher plaice cpue

Modern otter trawlers have lower plaice cpue than old sailing trawlers, and far lower than old steam otter trawlers

Implications for capacity EU trawler fleet• Marked discrepancies between long-term

changes plaice fishing power and cpue

• In spite of similar biomasses 1920s and 2000s!

• Limited nature of North Sea marine living resources

• Implication: much reduced international fleet probably capable of catching the same quantities of fish!