Sources for Dutch herring fishery in the North Sea, 1600-1850
In our lifetime, the North Sea herring fisheries have earned the attention from fishermen, marine biologists, regulators and consumers. For the time being the herring fishery appear to be quite successfully regulated, but do we really know what the future will be, in the event of climate changes? Answering this question as an historian this paper will attempt to show, how one can dig into the past in order to establish empirical relationship between climate and long-term dynamics of the North Sea herring population.
I would like to present how sources relating to the Dutch North Sea herring fishery from 1600-1850 might detect possible climatically induced changes in population size and distribution pattern of North Sea herring in this period.
Now, what makes the Dutch herring fishery particularly interesting is mainly two factors. First of all, this was the most important and geographically dispersed pre-industrial fishery in the North Sea area. Secondly, the nature of this fishery has helped produce a staggering number of historical records on catches and fishing effort. Therefore, it is possible to make time series of this particular fishery spanning several hundred years.
Methodology
The focal point and primary cause for creating time series, is to enable an indexation of the catch pr unit effort for the abovementioned fisheries in order to properly compare them with each other. By correlating Catch pr unit effort for the different herring fisheries over the period 1600-1850 I hope to examine whether, there are tendencies, which can be related to climatic changes such as those linked to the North Atlantic Oscillation. Especially for herring, it is very likely that climatic changes are responsible for large fluctuations in the stocks, as previously pointed out by marine scientists, Jürgen Alheit, Ad Corten and Brian McKenzie.
The Dutch buss fishery
Herring was the single most profitable commodity in Northern Europe from The Late Middle Ages onwards, and therefore a treasured object of taxation and thereby regulation. Most countries around the North Sea took part in the herring fishery, but no one developed an enterprise of the scale of the Dutch. In many ways the Dutch herring fishery was the first modern fishery in the sense that the operation was highly capitalised and well organised. In the 14th century the Dutch invented a technique for processing the herring on board, so they could stay out at sea fishing for more than a month until the boat was full. From the end of the 16th century until 1855, the so-called, College of the Great Fishery, conducted a virtual monopoly over the landing and processing of salted herring. In between 5-8 towns at a time had the privilege of taking part in the fishery, and therefore kept a register with incoming ships.
Enkhuizen and Schiedam
I have chosen the registers from the towns of Enkhuizen and Schiedam as the testing ground for the analysis. Schiedam is representative for the larger part of the towns in the herring fisheries, which were located at the mouth of the river Maas, in the heart of the economic centre of northern Europe in the early modern period. Enkhuizen on the contrary is located in the north-western most part of Holland, within a less urbanised economic landscape. However both towns distinguish themselves by offering uninterrupted data from 1600-1850. But how then, is it possible to use these accounts as a proxy for what when on at sea?
Lastgeldregisters as a source
The registers gives information on (i) the date of arrival of each individual ship, (ii) the size of the catch in barrels, (iii) tax paid per barrel, (iiii) the name and age of the skipper and for the register of Schiedam there is often information on the (v) number of fish which went into a barrel at different times of the season, and a specification on whether the herring had spawned or not. In terms of aggregating into cpue the conservative nature of the operation, makes it plausible that the size of the boat, as well as the size and operation of the gear remained stable from at least 1600-1850.
Seasonal variation
The lastgeldregisters from Enkhuizen show that it is possible to find the seasonal variation in landings. This means that it is possible to do a catch per unit effort analysis of each journey of each herring bus, based on landings per day fishing, since the herring fisheries did not start until 24 June each year.
For the rest of the season stretching roughly until the end of February or some times into March, the same calculation of catch per day fishing can be done for the busses, where the name of the skipper reveal that it is the second or third journey of the season. – By putting in a constant of some days in between the homecoming of the first journey and the departure of the second, the time of fishing can be measured via the date of homecoming from the second or following journey.
1713-1723-1733
As an example, this graph shows the seasonal distribution of landings in Enkhuizen in 1713-14, 1723-24 and 1733-34. Each dot represents one arrival of a ship. The season actually start in the middle of the diagram in high summer and stretches to the right and back into the left side of the diagram. There is a common trend for the three years, in that the season opens with quite small catches, reflecting the high prices to be obtained at the start of the season. Thereafter, the busses carrying up to 30 lasts of herring returned when the boats were more or less full. It would seem that each skipper had roughly two voyages from summer until Christmas, and an extra voyage in winter. This means for instance, that the year of 1723 constituted a lot better year than 1733. The total catch per journey for the two years was the same – between 17-18 lasts for the whole year, but when the number of days fishing is taken into account, the cpue of 1723 was more than a third better than in 1733.
Where did they fish?
In order to split up the annual landings into ca. three periods, constituting a meaningful differentiation between natural phases of the seasonal variation of the herring, several things are required. First of all, it is necessary to know where the fishermen went fishing in the time june-march. The best records of this seem to be the logbooks of Dutch warships of convoying fishermen. – They need to be systematically analysed trying to estimate the routes and schedules for the convoy ships as well as sightings or other information with direct regard to the herring busses. In the event of a successful outcome of this, I will try to draw a grid for the seasonal movement of the convoy ships i.e. fishermen, whom one must assume, follows the migration patterns of the different herring populations roughly starting in Scotland/Orkneys in the summer then fishing more and more to the south along the English coastline and Dogger Bank, finally ending up in the English Channel in the winter months. The more data on this, which becomes available, the more trustworthy are the grids. Other sources for this could be random annotations in the registers of landed fish. I believe an interesting aspect of this spatial stratification would be to compare the development, over time, of different sub-populations of herring in the areas mentioned. However, how small or large do these grids need to be, in order to allow for the testing of my hypotheses?
Questions for biologists:
In his dissertation, Herring and Climate, Ad Corten of RIVO in The Netherlands concluded that changes in the distribution of North Sea herring were related to a number of different environmental variables, including:
- Atlantic inflow into the north western North Sea as reflected by the Metridia Cancacia index for this area
- Water temperature in February in the north eastern North Sea
- Annual abundance of calanus finmarchicus in the total North Sea
- Abundance of Calanus finmarchicus in the north eastern North Sea in June
- Northeasterly winds over the Skagerrak in autumn
Now, the results of Corten seem convincing within their own context being the latter half of the 20th century, but will they stand the test of century long timescales? In order to answer this question, ladies and gentlemen, I need your help. – First of all, how far back in time is it possible to find data on the climatic indicators mentioned, and secondly what will it take to make the data comparable to my historical data? If possible I think we can really document empirical relationships between climate and long-term dynamics of aquatic ecosystems.
More information: PhD-stipend, Bo Poulsen, Centre for Maritime and Regional Studies, University of Southern Denmark http://www.cmrs.dk