A scientific analysis of a sport fishery

​The Shimoni sport fishery has one of the most, if not the most detailed and extensive databases of any fishery in the world, let alone a sport fishery, covering just over 50 years. Adding value to this the databases have been recorded by only two people, Pat and Simon Hemphill.

My father, Pat Hemphill is a legend of the Kenya sport fishing scene having first opened the famous Pemba Channel Fishing Club in December 1962. As from July 1963 he maintained a very detailed logbook recording every day that was fished. Every fish, however big or small was documented providing numbers and weights. For the smaller species total numbers and weights were provided whilst individual weights of the billfish, sharks and tunas of more than 50 pounds were listed. Billfish catches made by visiting boats were also recorded.

Until the late 1980’s the fishery was basically a take fishery where every fish that was caught was landed and brought back to the club for weighing. Nothing was wasted though; every fish had a market and was sold through the local dealers. In those days the proceeds for any fish sold were credited against the client’s account so that in more than one occasion a client actually made a profit on his charter fee. This was a very unusual practise, and, in many cases, clients would actually put their fish proceeds to the local community project that was being supported by my parents. 

Apart from the weights and numbers of all fish landed against the individual boats the names of the client along with weather/sea conditions and the sightings of anything unusual was also documented
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In addition, Pat was also a great proponent of the rules of the fishery as provided by the International Game Fish Association (IGFA). In Africa there is the regional body, the Game Fish Association of Africa (GFUA) and locally the Kenya Association of Sea Angling Clubs (KASAC) later to become the Kenya Association of Sea Anglers (KASA). These organizations maintain World, African and Kenyan angling records respectively. My father was one of the original founders and a long-term chairman of KASAC.

Ever since I was a small boy growing up, I couldn’t help but be addicted to the sport with a fascination for marlin. There was a large board in the clubhouse at Shimoni depicting all the angling records, which was largely kept up by myself. Upon my return from university in the UK in July 1981 where I received an honours degree in zoology with marine zoology, I joined the business. The scientist in me had so many questions that I wanted answers to and so I extended the database.

From July 1981 onwards I maintained a very detailed diary in which I recorded everything that happened out at sea, which was helped by the regular radio callups between the fleet. From the moment that VHF became available and before that CB radio my father had established a regular radio call up for all boats fishing within the Pemba Channel on the hour every hour and this practise continues to the present day.

That 1981 fishing season was a great season to start with, the tuna fishing was great and there were plenty of billfish of all species. With so many yellowfin tuna of different sizes I began to collect data recording the detailed morphological measurements, stomach contents and sexes of all yellowfin and billfishes. In response to a letter that I had written to Dr Tony Pitcher at Bangor University, later to become Professor of Fisheries at the University of British Columbia asking what I might do with all this data he replied write a PhD. And, that is exactly what I did looking into the ageing, feeding and sexual development of the yellowfin tuna along with the tuna fishery as part of a multispecies fishery. 

Although the logbook initiated by my father continues to be maintained the diaries contain a raft of additional data. The weather and sea conditions have been recorded as they change throughout the day. Every billfish that has been sighted has been recorded and where possible for marlin their GPS coordinates. A complete list of factors recorded is provided below but at this point I am in the process of transferring the data into five different databases in Excel and have so far input from July 1992 to December 15, 1998. There is still a long way to go but so much interesting stuff that may be gleaned from this.
Database 1 – this is specifically for marlin caught aboard boats that have been skippered by me personally, Kamara, Kamara II and occasionally Broadbill where I can be certain of the authenticity of the data. Also, because I was the skipper information of what the fish was raised or caught on could be recorded. So that for every marlin that has been sighted we can record how it was first seen, including whether it was seen free jumping, tailing or just simply raised into the spread. What that fish was raised on, the size, type, colour and position of the bait or lure within the spread. What happened then and what did it finally take or not take.

Also recorded was the time of the sighting from which we can add tidal information plus the weather and sea conditions at that time have also been documented. 

Database 2 – this is for the fleet overall, the daily sightings and catches of each boat with general weather and sea conditions. Sightings of the larger sharks, such as tiger, mako and hammerhead have also been listed. This database relies on the skipper of each boat reporting accurately and honestly on the radio what they saw and caught during the day. 

Database 3 – records what each boat reported in terms of marlin or sailfish on the individual radio call ups during the day. From this we can look at the patterns throughout the day allied to lunar and tidal data.

Database 4 – this is a marlin database looking at each fish against the respective boat reporting the sighting, strike, loss or catch. 

From the recorded data and these databases there are many questions that we can seek answers to, including:

• Document the multispecies nature of the Shimoni sport fishery in conjunction with the overall Kenyan sport fishery. There have been species changes in the fishery, the most recent of which is blue marlin, which has seemingly become far more common in recent years.
• How has the fleet changed over 50+ years and what effect have these changes had on the fishery?
• Technological changes, especially the introduction of GPS and depth sounders have had a massive impact on the sport and in the analysis of any fishery these changes must somehow be recognised. Too often these along with other developments within the fisheries have been ignored during scientific analyses simply because scientists don’t know how to quantify these changes. The consequences of ignoring these factors have been to the detriment of many species, including tunas.
• Every sport fisher is aware of the developments in equipment over these past five decades, including the fishing rods and reels, lines, lures, hooks and virtually everything else that we use or may like to use. To this we must add developments in the boats and engines, which have also had a significant impact on the fisheries. Again, this needs to be taken into consideration because when we see great catches now is that because there are more fish or are, we simply becoming better at finding and catching them?
• Using a dataset of this nature we can analyse the effect of the lunar cycle and the impact that tides may have on catches even far offshore. 
• We can analyse the effect of time of day, different weather conditions and to what extent colour may play a role in a marlin’s selection of a food item. 
• When a marlin is sighted tailing what is the probability that it will come into the spread, and take?

These are just some of the questions that we may like to seek answers to but there are always going to be many more. Fishing to me has always been about science, understanding why something works, and even more importantly why sometimes we fail. On Kamara the relationship that I had with Hamisi who worked with me for more than 30 years was a very special one. Whenever we lost a fish, we would hold a debrief session to ascertain what may have been the reason and how can we protect against it happening again.
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I shall be writing more notes in this section so please keep checking back.
Tight lines